diff --git a/backend/handlers/payments/giftcards.go b/backend/handlers/payments/giftcards.go
index 1ce6d40..195e3cb 100644
--- a/backend/handlers/payments/giftcards.go
+++ b/backend/handlers/payments/giftcards.go
@@ -1183,8 +1183,10 @@ func BuyGiftCard(w http.ResponseWriter, r *http.Request) {
 			}
 			recipient = userEmail
 		}
-		// TODO: send gift card code via email to recipient once SMTP is wired
-		log.Printf("GIFT CARD FOR FRIEND — code: %s, value: £%.2f, intended for: %s", cardID, amountPounds, recipient)
+		// TODO: send gift card code via email to recipient once SMTP is wired.
+		// Do NOT log the spendable gift-card code — it is a credential (12-digit
+		// code anyone can redeem). Log only the value and recipient for audit.
+		log.Printf("Gift card purchased for friend — value: £%.2f, intended for: %s (code stored in DB, not logged)", amountPounds, recipient)
 
 		_, err = db.Conn.Exec(ctx, `
 			INSERT INTO gift_card_transactions (gift_card_id, transaction_type, amount, reference_type, reference_id, user_id, notes)
diff --git a/backend/handlers/payments/handlers.go b/backend/handlers/payments/handlers.go
index 8ff3c8c..c022ecd 100644
--- a/backend/handlers/payments/handlers.go
+++ b/backend/handlers/payments/handlers.go
@@ -355,7 +355,14 @@ func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 		amount = *req.OverrideAmount
 	}
 
-	idempotencyKey := bookingID + "-" + req.PaymentType + "-" + strconv.FormatInt(amount, 10)
+	// Idempotency key for the payment. Cash/giftcard terminal payments are
+	// always fresh admin actions (not network-retryable), and the request has
+	// no client key — so a deterministic booking+type+amount key would wrongly
+	// dedup two legitimate identical payments (e.g. two £50 cash receipts on
+	// one booking). Use a unique key per payment: retries of a lost response
+	// are handled by the Square-side key for card payments, and cash/giftcard
+	// are DB-committed synchronously.
+	idempotencyKey := uniqueTipKey()
 
 	// Route based on payment method
 	if req.PaymentMethod != nil && (*req.PaymentMethod == "cash" || *req.PaymentMethod == "giftcard") {
@@ -412,10 +419,10 @@ func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 		if *req.PaymentMethod == "cash" {
 			err = tx.QueryRow(r.Context(), `
 				INSERT INTO payments (
-					booking_id, payment_type, payment_method, status, amount, created_by, created_at, updated_at
-				) VALUES ($1, $2, 'cash', 'completed', $3, $4, NOW(), NOW())
+					booking_id, payment_type, payment_method, status, amount, idempotency_key, created_by, created_at, updated_at
+				) VALUES ($1, $2, 'cash', 'completed', $3, $4, $5, NOW(), NOW())
 				RETURNING id
-			`, bookingID, req.PaymentType, amountPounds, adminID).Scan(&paymentID)
+			`, bookingID, req.PaymentType, amountPounds, idempotencyKey, adminID).Scan(&paymentID)
 			if err != nil {
 				log.Printf("Failed to create cash payment record: %v", err)
 				http.Error(w, "internal server error", http.StatusInternalServerError)
@@ -507,10 +514,10 @@ func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 
 			err = tx.QueryRow(r.Context(), `
 				INSERT INTO payments (
-					booking_id, payment_type, payment_method, status, amount, created_by, created_at, updated_at
-				) VALUES ($1, $2, 'giftcard', 'completed', $3, $4, NOW(), NOW())
+					booking_id, payment_type, payment_method, status, amount, idempotency_key, created_by, created_at, updated_at
+				) VALUES ($1, $2, 'giftcard', 'completed', $3, $4, $5, NOW(), NOW())
 				RETURNING id
-			`, bookingID, req.PaymentType, amountPounds, adminID).Scan(&paymentID)
+			`, bookingID, req.PaymentType, amountPounds, idempotencyKey, adminID).Scan(&paymentID)
 			if err != nil {
 				log.Printf("Failed to create giftcard payment record: %v", err)
 				http.Error(w, "internal server error", http.StatusInternalServerError)
@@ -1555,9 +1562,7 @@ func DeletePaymentMethod(w http.ResponseWriter, r *http.Request) {
 }
 
 type CreatePaymentMethodRequest struct {
-	CardNumber string `json:"card_number" validate:"required"`
-	Expiry     string `json:"expiry" validate:"required"`
-	CVC        string `json:"cvc" validate:"required"`
+	CardToken string `json:"card_token" validate:"required"`
 }
 
 func CreatePaymentMethod(w http.ResponseWriter, r *http.Request) {
@@ -1579,16 +1584,13 @@ func CreatePaymentMethod(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// M8
-	// L5
-
-	if req.CardNumber == "" || req.Expiry == "" || req.CVC == "" {
-		http.Error(w, "Card number, expiry, and CVC are required", http.StatusBadRequest)
+	if req.CardToken == "" {
+		http.Error(w, "card_token is required — use a Square Web Payments nonce", http.StatusBadRequest)
 		return
 	}
 
 	service := NewPaymentService()
-	card, err := service.CreatePaymentMethodFromDetails(r.Context(), userID, req.CardNumber, req.Expiry, req.CVC)
+	card, err := service.CreatePaymentMethodFromToken(r.Context(), userID, req.CardToken)
 	if err != nil {
 		if strings.Contains(err.Error(), "invalid") || strings.Contains(err.Error(), "expired") {
 			log.Printf("Failed to process request: %v", err)
@@ -1667,15 +1669,63 @@ func RefundPayment(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if req.Amount+alreadyRefunded > int64(payment.Amount*100) {
+	if req.Amount+alreadyRefunded > int64(math.Round(payment.Amount*100)) {
 		http.Error(w, "Refund amount exceeds payment amount", http.StatusBadRequest)
 		return
 	}
 
-	// Begin a transaction so that the Square refund and the DB record are
-	// atomically linked. If the commit fails after Square processes the refund,
-	// a CRITICAL log alerts monitoring — the Square refund cannot be reversed,
-	// but the DB record can be recreated from the log.
+	// Serialize refund attempts per payment to prevent two concurrent refunds
+	// both passing the over-refund guard and both charging Square. Mirrors the
+	// tip/gift-card advisory-lock pattern.
+	refundLockKey := paymentID
+	pinConn, err := db.Conn.Acquire(r.Context())
+	if err != nil {
+		log.Printf("Failed to acquire connection for refund lock: %v", err)
+		http.Error(w, "internal server error", http.StatusInternalServerError)
+		return
+	}
+	defer pinConn.Release()
+	if _, err := pinConn.Exec(r.Context(), `
+		SELECT pg_advisory_lock(hashtext('crussell:refund:' || $1))
+	`, refundLockKey); err != nil {
+		log.Printf("Failed to acquire refund serialization lock for %s: %v", paymentID, err)
+		http.Error(w, "internal server error", http.StatusInternalServerError)
+		return
+	}
+	defer func() {
+		if _, err := pinConn.Exec(context.Background(), `
+			SELECT pg_advisory_unlock(hashtext('crussell:refund:' || $1))
+		`, refundLockKey); err != nil {
+			log.Printf("Failed to release refund serialization lock for %s: %v", paymentID, err)
+		}
+	}()
+
+	// Deterministic idempotency key so a same-key retry (network timeout)
+	// does not create a second Square refund.
+	idempotencyKey := paymentID + "-refund-" + strconv.FormatInt(req.Amount, 10)
+
+	// Check for an existing refund with this key — dedup completed refunds.
+	var existingRefundStatus sql.NullString
+	err = db.Conn.QueryRow(r.Context(), `SELECT status FROM refunds WHERE idempotency_key = $1`, idempotencyKey).Scan(&existingRefundStatus)
+	if err == nil && existingRefundStatus.String == "completed" {
+		if err := json.NewEncoder(w).Encode(RefundResponse{
+			PaymentID: paymentID,
+			Amount:    req.Amount,
+			Status:    "completed",
+			Reason:    req.Reason,
+			CreatedAt: clock.Now().Format(time.RFC3339),
+		}); err != nil {
+			log.Printf("Failed to encode JSON response: %v", err)
+		}
+		return
+	}
+	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
+		log.Printf("Failed to check refund idempotency: %v", err)
+	}
+
+	// Begin a transaction. Insert the refund record as 'pending' first, commit,
+	// then call Square — so a Square failure leaves a retryable pending refund
+	// (reprocessed by the scheduler in refunds.go).
 	tx, err := db.Conn.Begin(r.Context())
 	if err != nil {
 		log.Printf("Failed to begin transaction for refund: %v", err)
@@ -1688,44 +1738,56 @@ func RefundPayment(w http.ResponseWriter, r *http.Request) {
 		}
 	}()
 
+	var refundID string
+	err = tx.QueryRow(r.Context(), `
+		INSERT INTO refunds (payment_id, booking_id, amount, status, reason, idempotency_key, created_by, created_at)
+		VALUES ($1, $2, $3, 'pending', $4, $5, $6, $7)
+		RETURNING id
+	`,
+		paymentID,
+		payment.BookingID,
+		float64(req.Amount)/100.0,
+		req.Reason,
+		idempotencyKey,
+		adminID,
+		clock.Now(),
+	).Scan(&refundID)
+	if err != nil {
+		log.Printf("Failed to create pending refund record: %v", err)
+		http.Error(w, "internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if err := tx.Commit(r.Context()); err != nil {
+		log.Printf("Failed to commit refund transaction: %v", err)
+		http.Error(w, "internal server error", http.StatusInternalServerError)
+		return
+	}
+
 	refundReq := square.RefundPaymentReq{
 		PaymentID:      *payment.SquarePaymentID,
 		Amount:         req.Amount,
-		IdempotencyKey: paymentID + "-" + strconv.FormatInt(req.Amount, 10),
+		IdempotencyKey: idempotencyKey,
 		Reason:         req.Reason,
 	}
 
 	refundResult, err := SquareClient.RefundPayment(r.Context(), refundReq)
 	if err != nil {
-		log.Printf("Failed to refund payment: %v", err)
+		// Refund record intentionally left as 'pending' for the scheduler to
+		// re-attempt (refunds.go ProcessPendingSquareRefunds).
+		log.Printf("Failed to refund payment (refund %s left pending): %v", refundID, err)
 		http.Error(w, "Refund failed", http.StatusInternalServerError)
 		return
 	}
 
 	squareRefundID := refundResult.ID
 
-	var refundID string
-	err = tx.QueryRow(r.Context(), `
-		INSERT INTO refunds (payment_id, booking_id, amount, square_refund_id, status, reason, created_by, created_at)
-		VALUES ($1, $2, $3, $4, 'completed', $5, $6, $7)
-		RETURNING id
-	`,
-		paymentID,
-		payment.BookingID,
-		float64(req.Amount)/100.0,
-		squareRefundID,
-		req.Reason,
-		adminID,
-		clock.Now(),
-	).Scan(&refundID)
-	if err != nil {
-		log.Printf("Failed to create refund record: %v", err)
-		http.Error(w, "internal server error", http.StatusInternalServerError)
-		return
-	}
-
-	if err := tx.Commit(r.Context()); err != nil {
-		log.Printf("CRITICAL: Refund committed by Square (%s) but DB transaction failed — refund record %s may be missing: %v", squareRefundID, refundID, err)
+	// Square succeeded — update the refund record to completed.
+	if _, upErr := db.Conn.Exec(r.Context(),
+		`UPDATE refunds SET status = 'completed', square_refund_id = $1 WHERE id = $2`,
+		squareRefundID, refundID,
+	); upErr != nil {
+		log.Printf("CRITICAL: Square refund committed (%s) but DB update for refund %s failed — manual reconciliation required: %v", squareRefundID, refundID, upErr)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -2089,7 +2151,7 @@ func GetBookingPaymentSummary(w http.ResponseWriter, r *http.Request) {
 			BookingID:   p.BookingID,
 			PaymentType: p.PaymentType,
 			Status:      p.Status,
-			Amount:      int64(p.Amount * 100),
+			Amount:      int64(math.Round(p.Amount * 100)),
 			CardLast4:   p.CardLast4,
 			CreatedAt:   p.CreatedAt.Format(time.RFC3339),
 		}
@@ -2100,7 +2162,7 @@ func GetBookingPaymentSummary(w http.ResponseWriter, r *http.Request) {
 		refunds[i] = RefundResponse{
 			ID:        rf.ID,
 			PaymentID: rf.PaymentID,
-			Amount:    int64(rf.Amount * 100),
+			Amount:    int64(math.Round(rf.Amount * 100)),
 			Status:    rf.Status,
 			Reason:    rf.Reason,
 			CreatedAt: rf.CreatedAt.Format(time.RFC3339),
@@ -2108,12 +2170,12 @@ func GetBookingPaymentSummary(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if err := json.NewEncoder(w).Encode(PaymentSummaryResponse{
-		TotalAmount:     int64(summary.TotalAmount * 100),
-		PaidAmount:      int64(summary.PaidAmount * 100),
-		RefundedAmount:  int64(summary.RefundedAmount * 100),
-		RemainingAmount: int64(summary.RemainingAmount * 100),
-		TotalVATAmount:  int64(summary.TotalVATAmount * 100),
-		TotalNetAmount:  int64(summary.TotalNetAmount * 100),
+		TotalAmount:     int64(math.Round(summary.TotalAmount * 100)),
+		PaidAmount:      int64(math.Round(summary.PaidAmount * 100)),
+		RefundedAmount:  int64(math.Round(summary.RefundedAmount * 100)),
+		RemainingAmount: int64(math.Round(summary.RemainingAmount * 100)),
+		TotalVATAmount:  int64(math.Round(summary.TotalVATAmount * 100)),
+		TotalNetAmount:  int64(math.Round(summary.TotalNetAmount * 100)),
 		Payments:        payments,
 		Refunds:         refunds,
 	}); err != nil {
diff --git a/backend/handlers/payments/payments_test.go b/backend/handlers/payments/payments_test.go
index 0c663d5..e8f4da1 100644
--- a/backend/handlers/payments/payments_test.go
+++ b/backend/handlers/payments/payments_test.go
@@ -595,6 +595,60 @@ func TestRefund_FullRefund(t *testing.T) {
 	}
 }
 
+func TestRefund_SameKeyRetry_Dedups(t *testing.T) {
+	// A retry of the same refund (network timeout, double-click) must not
+	// create a second Square refund or a second DB row — the idempotency key
+	// (paymentID + amount) dedups it.
+	t.Parallel()
+	ctx, tx := testutils.SetupTestTx(t)
+
+	_, bookingID, _ := setupTestData(t, ctx, tx)
+
+	adminID, err := fixtures.CreateTestAdminUser(tx)
+	if err != nil {
+		t.Fatalf("failed to create admin user: %v", err)
+	}
+
+	adminToken := jwt.GenerateTestToken(adminID, "admin")
+
+	paymentID, err := fixtures.CreateTestPayment(tx, bookingID, 5000.00, "in_person_card", "full", "completed")
+	if err != nil {
+		t.Fatalf("failed to create payment: %v", err)
+	}
+	_, err = tx.Exec(ctx, "UPDATE payments SET square_payment_id = 'sqp_test_dedup' WHERE id = $1", paymentID)
+	if err != nil {
+		t.Fatalf("failed to update payment: %v", err)
+	}
+
+	req := RefundRequest{
+		Amount: 5000,
+		Reason: "customer request",
+	}
+
+	handler := RefundPayment
+	// First refund — completes.
+	w1 := makePaymentRequest(handler, "POST", "/api/admin/payments/"+paymentID+"/refund", req, adminToken, ctx)
+	if w1.Code != http.StatusOK {
+		t.Fatalf("first refund: expected 200, got %d. body: %s", w1.Code, w1.Body.String())
+	}
+
+	// Same-key retry (identical amount, reason) — must dedup, not double-refund.
+	w2 := makePaymentRequest(handler, "POST", "/api/admin/payments/"+paymentID+"/refund", req, adminToken, ctx)
+	if w2.Code != http.StatusOK {
+		t.Fatalf("retry refund: expected 200, got %d. body: %s", w2.Code, w2.Body.String())
+	}
+
+	// Exactly one refund row for this payment.
+	var refundCount int
+	err = tx.QueryRow(ctx, `SELECT COUNT(*) FROM refunds WHERE payment_id = $1`, paymentID).Scan(&refundCount)
+	if err != nil {
+		t.Fatalf("failed to query refunds: %v", err)
+	}
+	if refundCount != 1 {
+		t.Errorf("expected 1 refund row (deduped), got %d", refundCount)
+	}
+}
+
 func TestRefund_PartialRefund(t *testing.T) {
 	t.Parallel()
 	ctx, tx := testutils.SetupTestTx(t)
@@ -2304,21 +2358,36 @@ func TestCreatePaymentMethod_HappyPath(t *testing.T) {
 
 	handler := CreatePaymentMethod
 	reqBody := CreatePaymentMethodRequest{
-		CardNumber: "4111111111111111",
-		Expiry:     "12/30",
-		CVC:        "123",
+		CardToken: "cnon:visa",
 	}
 
 	w := makePaymentRequest(handler, "POST", "/api/user/payment-methods", reqBody, token, ctx)
 
-	// PCI-DSS parity: raw PAN card creation is blocked in production, so the
-	// mock must reject it too — otherwise dev testing masks a prod failure.
-	if w.Code != http.StatusInternalServerError {
-		t.Errorf("expected status 500 (raw PAN rejected), got %d. body: %s", w.Code, w.Body.String())
+	if w.Code != http.StatusOK {
+		t.Errorf("expected status 200, got %d. body: %s", w.Code, w.Body.String())
+		return
+	}
+
+	var card SavedCard
+	if err := json.Unmarshal(w.Body.Bytes(), &card); err != nil {
+		t.Fatalf("failed to parse response: %v", err)
+	}
+	if card.Brand != "VISA" {
+		t.Errorf("expected brand VISA, got %s", card.Brand)
+	}
+	if card.Last4 != "1111" {
+		t.Errorf("expected last4 1111, got %s", card.Last4)
+	}
+	if !card.IsDefault {
+		t.Error("expected first card to be default")
 	}
 }
 
-func TestCreatePaymentMethod_ExpiredCardRejected(t *testing.T) {
+func TestCreatePaymentMethod_RawPANRejected(t *testing.T) {
+	// PCI-DSS: raw PANs are never accepted at the API edge — the handler must
+	// return 400 for a card_number body, since the field no longer exists and
+	// card_token is required. Validates that a raw PAN never reaches the
+	// Square client.
 	t.Parallel()
 	ctx, tx := testutils.SetupTestTx(t)
 
@@ -2329,55 +2398,17 @@ func TestCreatePaymentMethod_ExpiredCardRejected(t *testing.T) {
 
 	token := jwt.GenerateUserToken(userID)
 
+	// Raw PAN sent as the old field name — should be ignored and rejected.
 	handler := CreatePaymentMethod
-	reqBody := CreatePaymentMethodRequest{
-		CardNumber: "4111111111111111",
-		Expiry:     "01/20",
-		CVC:        "123",
+	reqBody := map[string]string{
+		"card_number": "4111111111111111",
+		"expiry":      "12/30",
+		"cvc":         "123",
 	}
 
 	w := makePaymentRequest(handler, "POST", "/api/user/payment-methods", reqBody, token, ctx)
-
 	if w.Code != http.StatusBadRequest {
-		t.Errorf("expected status 400, got %d. body: %s", w.Code, w.Body.String())
-	}
-}
-
-func TestCreatePaymentMethod_InvalidExpiryRejected(t *testing.T) {
-	t.Parallel()
-	ctx, tx := testutils.SetupTestTx(t)
-
-	userID, err := fixtures.CreateTestUser(tx)
-	if err != nil {
-		t.Fatalf("failed to create test user: %v", err)
-	}
-
-	token := jwt.GenerateUserToken(userID)
-
-	tests := []struct {
-		name   string
-		expiry string
-	}{
-		{"bad format", "12-30"},
-		{"bad month", "13/30"},
-		{"bad year", "12/abc"},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			handler := CreatePaymentMethod
-			reqBody := CreatePaymentMethodRequest{
-				CardNumber: "4111111111111111",
-				Expiry:     tt.expiry,
-				CVC:        "123",
-			}
-
-			w := makePaymentRequest(handler, "POST", "/api/user/payment-methods", reqBody, token, ctx)
-
-			if w.Code != http.StatusBadRequest {
-				t.Errorf("expected status 400, got %d. body: %s", w.Code, w.Body.String())
-			}
-		})
+		t.Errorf("expected status 400 (card_token required), got %d. body: %s", w.Code, w.Body.String())
 	}
 }
 
@@ -2396,9 +2427,7 @@ func TestCreatePaymentMethod_MissingFieldsRejected(t *testing.T) {
 		name string
 		body CreatePaymentMethodRequest
 	}{
-		{"no card number", CreatePaymentMethodRequest{Expiry: "12/30", CVC: "123"}},
-		{"no expiry", CreatePaymentMethodRequest{CardNumber: "4111111111111111", CVC: "123"}},
-		{"no cvc", CreatePaymentMethodRequest{CardNumber: "4111111111111111", Expiry: "12/30"}},
+		{"no card token", CreatePaymentMethodRequest{}},
 	}
 
 	for _, tt := range tests {
@@ -2419,9 +2448,7 @@ func TestCreatePaymentMethod_NoAuthRejected(t *testing.T) {
 
 	handler := CreatePaymentMethod
 	w := makePaymentRequest(handler, "POST", "/api/user/payment-methods", CreatePaymentMethodRequest{
-		CardNumber: "4111111111111111",
-		Expiry:     "12/30",
-		CVC:        "123",
+		CardToken: "cnon:visa",
 	}, "", ctx)
 
 	if w.Code != http.StatusUnauthorized {
@@ -2440,18 +2467,36 @@ func TestCreatePaymentMethod_SecondCardNotDefault(t *testing.T) {
 
 	token := jwt.GenerateUserToken(userID)
 
-	// PCI-DSS parity: raw PAN card creation is blocked in production, so the
-	// mock must reject it too — otherwise dev testing masks a prod failure.
+	// Create first card
 	handler := CreatePaymentMethod
 	reqBody := CreatePaymentMethodRequest{
-		CardNumber: "4111111111111111",
-		Expiry:     "12/30",
-		CVC:        "123",
+		CardToken: "cnon:visa",
 	}
 
 	w := makePaymentRequest(handler, "POST", "/api/user/payment-methods", reqBody, token, ctx)
-	if w.Code != http.StatusInternalServerError {
-		t.Fatalf("expected 500 (raw PAN rejected), got %d. body: %s", w.Code, w.Body.String())
+	if w.Code != http.StatusOK {
+		t.Fatalf("failed to create first card: %d. body: %s", w.Code, w.Body.String())
+	}
+
+	reqBody2 := CreatePaymentMethodRequest{
+		CardToken: "cnon:mastercard",
+	}
+
+	w = makePaymentRequest(handler, "POST", "/api/user/payment-methods", reqBody2, token, ctx)
+	if w.Code != http.StatusOK {
+		t.Fatalf("failed to create second card: %d. body: %s", w.Code, w.Body.String())
+	}
+
+	var card SavedCard
+	if err := json.Unmarshal(w.Body.Bytes(), &card); err != nil {
+		t.Fatalf("failed to parse response: %v", err)
+	}
+
+	if card.Brand != "MASTERCARD" {
+		t.Errorf("expected brand MASTERCARD, got %s", card.Brand)
+	}
+	if card.IsDefault {
+		t.Error("expected second card to NOT be default")
 	}
 }
 
diff --git a/backend/handlers/payments/service.go b/backend/handlers/payments/service.go
index 8932848..9cded59 100644
--- a/backend/handlers/payments/service.go
+++ b/backend/handlers/payments/service.go
@@ -10,8 +10,7 @@ import (
 	"fmt"
 	"log"
 	"log/slog"
-	"strconv"
-	"strings"
+	"math"
 	"time"
 
 	"github.com/jackc/pgx/v5"
@@ -359,7 +358,7 @@ func (s *PaymentService) GetAlreadyRefundedAmount(ctx context.Context, paymentID
 	if err != nil {
 		return 0, err
 	}
-	return int64(amount * 100), nil
+	return int64(math.Round(amount * 100)), nil
 }
 
 func (s *PaymentService) HasCompletedPayment(ctx context.Context, bookingID string) (bool, error) {
@@ -501,29 +500,11 @@ func (s *PaymentService) DeletePaymentMethod(ctx context.Context, cardID, userID
 	return nil
 }
 
-func (s *PaymentService) CreatePaymentMethodFromDetails(ctx context.Context, userID, cardNumber, expiry, cvc string) (*SavedCard, error) {
-	parts := strings.Split(expiry, "/")
-	if len(parts) != 2 {
-		return nil, errors.New("invalid expiry format, use MM/YY")
-	}
-	expMonth, err := strconv.Atoi(parts[0])
-	if err != nil || expMonth < 1 || expMonth > 12 {
-		return nil, errors.New("invalid expiry month")
-	}
-	expYear, err := strconv.Atoi(parts[1])
-	if err != nil || expYear < 0 || expYear > 99 {
-		return nil, errors.New("invalid expiry year")
-	}
-	expYear += 2000
-
-	// Check if card is expired
-	now := clock.Now()
-	expiryDate := time.Date(expYear, time.Month(expMonth), 1, 0, 0, 0, 0, time.UTC)
-	if expiryDate.Before(now) {
-		return nil, errors.New("card has expired")
-	}
-
-	cardOnFile, err := SquareClient.CreateCardOnFileRaw(ctx, userID, cardNumber, expMonth, expYear, cvc)
+func (s *PaymentService) CreatePaymentMethodFromToken(ctx context.Context, userID, cardToken string) (*SavedCard, error) {
+	// PCI-DSS: raw PANs are never accepted. The client must supply a Square
+	// Web Payments nonce (cnon:xxx), which the backend tokenizes via the
+	// Cards API — the full PAN exists only inside Square's vault.
+	cardOnFile, err := SquareClient.CreateCardOnFile(ctx, userID, cardToken)
 	if err != nil {
 		return nil, fmt.Errorf("failed to tokenize card: %w", err)
 	}
@@ -535,7 +516,7 @@ func (s *PaymentService) CreatePaymentMethodFromDetails(ctx context.Context, use
 		SELECT $1, $2, $3, $4, $5, $6, $7,
 			NOT EXISTS(SELECT 1 FROM user_saved_cards WHERE user_id = $1 AND deleted_at IS NULL)
 		RETURNING id, is_default
-	`, userID, cardOnFile.CardID, cardOnFile.Brand, cardOnFile.Last4, expMonth, expYear, cardOnFile.Fingerprint).Scan(&savedCardID, &isDefault)
+	`, userID, cardOnFile.CardID, cardOnFile.Brand, cardOnFile.Last4, cardOnFile.ExpMonth, cardOnFile.ExpYear, cardOnFile.Fingerprint).Scan(&savedCardID, &isDefault)
 	if err != nil {
 		return nil, fmt.Errorf("failed to save card: %w", err)
 	}
@@ -545,8 +526,8 @@ func (s *PaymentService) CreatePaymentMethodFromDetails(ctx context.Context, use
 		SquareCardID: cardOnFile.CardID,
 		Brand:        cardOnFile.Brand,
 		Last4:        cardOnFile.Last4,
-		ExpMonth:     expMonth,
-		ExpYear:      expYear,
+		ExpMonth:     cardOnFile.ExpMonth,
+		ExpYear:      cardOnFile.ExpYear,
 		Fingerprint:  cardOnFile.Fingerprint,
 		IsDefault:    isDefault,
 	}, nil
diff --git a/backend/handlers/payments/till.go b/backend/handlers/payments/till.go
index f751c43..674e99a 100644
--- a/backend/handlers/payments/till.go
+++ b/backend/handlers/payments/till.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"log"
 	"log/slog"
+	"math"
 	"net/http"
 
 	"crussell/db"
@@ -28,10 +29,7 @@ type TillSaleRequest struct {
 	UserSavedCardID *string `json:"user_saved_card_id,omitempty"`
 	UserID          *string `json:"user_id,omitempty"`
 	IdempotencyKey  string  `json:"idempotency_key,omitempty"`
-	CardNumber      string  `json:"card_number,omitempty"`
-	CardExpMonth    int     `json:"card_exp_month,omitempty"`
-	CardExpYear     int     `json:"card_exp_year,omitempty"`
-	CardCVC         string  `json:"card_cvc,omitempty"`
+	CardToken       string  `json:"card_token,omitempty"`
 	RedeemToUserID  *string `json:"redeem_to_user_id,omitempty"`
 }
 
@@ -94,8 +92,8 @@ func CreateTillSale(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "user_saved_card_id is required when payment method is saved_card", http.StatusBadRequest)
 		return
 	}
-	if req.PaymentMethod == "online_square" && req.CardNumber == "" {
-		http.Error(w, "card_number is required when payment method is online_square", http.StatusBadRequest)
+	if req.PaymentMethod == "online_square" && req.CardToken == "" {
+		http.Error(w, "card_token is required when payment method is online_square — use a Square Web Payments nonce", http.StatusBadRequest)
 		return
 	}
 	if req.Action == "topup" && (req.GiftCardID == nil || *req.GiftCardID == "") {
@@ -104,22 +102,33 @@ func CreateTillSale(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Idempotency check: if key provided, return existing sale if found
+	// Idempotency handling. A 'completed' sale is a dedup (return it). A
+	// 'pending' sale means the previous Square charge failed — the gift card
+	// was already funded in the committed transaction, so re-attempt the
+	// Square charge (Square dedups on the same key) and complete the sale.
+	// Mirrors the tip/gift-card pending-reuse pattern.
+	var existingPendingID string
+	var existingPendingGiftCard string
 	if req.IdempotencyKey != "" {
-		var existingID, existingStatus string
-		err := db.Conn.QueryRow(ctx, `SELECT id, status FROM till_sales WHERE idempotency_key = $1`, req.IdempotencyKey).Scan(&existingID, &existingStatus)
+		var existingID, existingStatus, existingItemID string
+		err := db.Conn.QueryRow(ctx, `SELECT id, status, item_id FROM till_sales WHERE idempotency_key = $1`, req.IdempotencyKey).Scan(&existingID, &existingStatus, &existingItemID)
 		if err == nil {
-			// Existing sale found — return its ACTUAL status (may be 'pending'
-			// if a previous Square charge failed; must not report 'completed').
-			if err := json.NewEncoder(w).Encode(TillSaleResponse{
-				ID:            existingID,
-				ItemType:      req.ItemType,
-				TotalAmount:   req.Amount,
-				PaymentMethod: req.PaymentMethod,
-				Status:        existingStatus,
-			}); err != nil {
-				log.Printf("Failed to encode JSON response: %v", err)
+			if existingStatus == "completed" {
+				if err := json.NewEncoder(w).Encode(TillSaleResponse{
+					ID:            existingID,
+					ItemType:      req.ItemType,
+					TotalAmount:   req.Amount,
+					PaymentMethod: req.PaymentMethod,
+					Status:        "completed",
+				}); err != nil {
+					log.Printf("Failed to encode JSON response: %v", err)
+				}
+				return
+			}
+			if existingStatus == "pending" {
+				existingPendingID = existingID
+				existingPendingGiftCard = existingItemID
 			}
-			return
 		}
 	}
 
@@ -137,96 +146,102 @@ func CreateTillSale(w http.ResponseWriter, r *http.Request) {
 		}
 	}()
 
+	// Pending-retry: the gift card was already created and funded in the prior
+	// committed transaction, so skip the create/top-up and sale-insert blocks.
 	var giftCardID string
-	if req.Action == "create" {
-		var purchaseVoucherType string
-		err = tx.QueryRow(ctx, `SELECT COALESCE(voucher_type, 'SPV') FROM business_settings LIMIT 1`).Scan(&purchaseVoucherType)
-		if err != nil {
-			log.Printf("Failed to query voucher type: %v", err)
-			http.Error(w, "internal server error", http.StatusInternalServerError)
-			return
-		}
-		if purchaseVoucherType == "" {
-			purchaseVoucherType = "SPV"
-		}
-		err = tx.QueryRow(ctx, `
+	if existingPendingID != "" {
+		giftCardID = existingPendingGiftCard
+	} else {
+		if req.Action == "create" {
+			var purchaseVoucherType string
+			err = tx.QueryRow(ctx, `SELECT COALESCE(voucher_type, 'SPV') FROM business_settings LIMIT 1`).Scan(&purchaseVoucherType)
+			if err != nil {
+				log.Printf("Failed to query voucher type: %v", err)
+				http.Error(w, "internal server error", http.StatusInternalServerError)
+				return
+			}
+			if purchaseVoucherType == "" {
+				purchaseVoucherType = "SPV"
+			}
+			err = tx.QueryRow(ctx, `
 			INSERT INTO gift_cards (total_funds_added, amount_remaining, created_by, is_inventory, voucher_type_at_purchase)
 			VALUES ($1, $1, $2, FALSE, $3)
 			RETURNING id
 		`, req.Amount, adminID, purchaseVoucherType).Scan(&giftCardID)
-		if err != nil {
-			log.Printf("Failed to create gift card: %v", err)
-			http.Error(w, "internal server error", http.StatusInternalServerError)
-			return
-		}
+			if err != nil {
+				log.Printf("Failed to create gift card: %v", err)
+				http.Error(w, "internal server error", http.StatusInternalServerError)
+				return
+			}
 
-		_, err = tx.Exec(ctx, `
+			_, err = tx.Exec(ctx, `
 			INSERT INTO gift_card_transactions (gift_card_id, transaction_type, amount, reference_type, reference_id, user_id, notes)
 			VALUES ($1, 'purchase', $2, 'till_sale', NULL, $3, NULL)
 		`, giftCardID, req.Amount, req.UserID)
-		if err != nil {
-			log.Printf("Failed to create gift_card_transaction: %v", err)
-			http.Error(w, "internal server error", http.StatusInternalServerError)
-			return
-		}
-	} else {
-		cardID := validators.NormalizeGiftCardCode(*req.GiftCardID)
-		var redeemedBy sql.NullString
-		err = tx.QueryRow(ctx, "SELECT redeemed_by FROM gift_cards WHERE id = $1", cardID).Scan(&redeemedBy)
-		if err != nil {
-			if errors.Is(err, pgx.ErrNoRows) {
-				http.Error(w, "Gift card not found", http.StatusNotFound)
+			if err != nil {
+				log.Printf("Failed to create gift_card_transaction: %v", err)
+				http.Error(w, "internal server error", http.StatusInternalServerError)
+				return
+			}
+		} else {
+			cardID := validators.NormalizeGiftCardCode(*req.GiftCardID)
+			var redeemedBy sql.NullString
+			err = tx.QueryRow(ctx, "SELECT redeemed_by FROM gift_cards WHERE id = $1", cardID).Scan(&redeemedBy)
+			if err != nil {
+				if errors.Is(err, pgx.ErrNoRows) {
+					http.Error(w, "Gift card not found", http.StatusNotFound)
+					return
+				}
+				log.Printf("Failed to check gift card: %v", err)
+				http.Error(w, "internal server error", http.StatusInternalServerError)
+				return
+			}
+			if redeemedBy.Valid {
+				http.Error(w, "Cannot top up a card that has been redeemed to an account", http.StatusBadRequest)
 				return
 			}
-			log.Printf("Failed to check gift card: %v", err)
-			http.Error(w, "internal server error", http.StatusInternalServerError)
-			return
-		}
-		if redeemedBy.Valid {
-			http.Error(w, "Cannot top up a card that has been redeemed to an account", http.StatusBadRequest)
-			return
-		}
 
-		var isInventory bool
-		var previousTotal float64
-		err = tx.QueryRow(ctx, `SELECT is_inventory, total_funds_added FROM gift_cards WHERE id = $1`, cardID).Scan(&isInventory, &previousTotal)
-		if err != nil {
-			log.Printf("Failed to check gift card state: %v", err)
-			http.Error(w, "internal server error", http.StatusInternalServerError)
-			return
-		}
+			var isInventory bool
+			var previousTotal float64
+			err = tx.QueryRow(ctx, `SELECT is_inventory, total_funds_added FROM gift_cards WHERE id = $1`, cardID).Scan(&isInventory, &previousTotal)
+			if err != nil {
+				log.Printf("Failed to check gift card state: %v", err)
+				http.Error(w, "internal server error", http.StatusInternalServerError)
+				return
+			}
 
-		_, err = tx.Exec(ctx, `
+			_, err = tx.Exec(ctx, `
 			UPDATE gift_cards
 			SET total_funds_added = total_funds_added + $1,
 			    amount_remaining = amount_remaining + $1,
 			    last_used_at = NOW()
 			WHERE id = $2
 		`, req.Amount, cardID)
-		if err != nil {
-			log.Printf("Failed to top up gift card: %v", err)
-			http.Error(w, "internal server error", http.StatusInternalServerError)
-			return
-		}
+			if err != nil {
+				log.Printf("Failed to top up gift card: %v", err)
+				http.Error(w, "internal server error", http.StatusInternalServerError)
+				return
+			}
 
-		transactionType := "topup"
-		var notes *string
-		if isInventory && previousTotal == 0 {
-			transactionType = "purchase"
-			n := "first top-up on inventory card"
-			notes = &n
-		}
-		_, err = tx.Exec(ctx, `
+			transactionType := "topup"
+			var notes *string
+			if isInventory && previousTotal == 0 {
+				transactionType = "purchase"
+				n := "first top-up on inventory card"
+				notes = &n
+			}
+			_, err = tx.Exec(ctx, `
 			INSERT INTO gift_card_transactions (gift_card_id, transaction_type, amount, reference_type, reference_id, user_id, notes)
 			VALUES ($1, $2, $3, 'till_sale', NULL, $4, $5)
 		`, cardID, transactionType, req.Amount, req.UserID, notes)
-		if err != nil {
-			log.Printf("Failed to create gift_card_transaction: %v", err)
-			http.Error(w, "internal server error", http.StatusInternalServerError)
-			return
-		}
+			if err != nil {
+				log.Printf("Failed to create gift_card_transaction: %v", err)
+				http.Error(w, "internal server error", http.StatusInternalServerError)
+				return
+			}
 
-		giftCardID = cardID
+			giftCardID = cardID
+		}
 	}
 
 	// If the gift card should be immediately redeemed to a user's account balance
@@ -260,7 +275,7 @@ func CreateTillSale(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	penceAmount := int64(req.Amount * 100)
+	penceAmount := int64(math.Round(req.Amount * 100))
 
 	var squarePaymentID *string
 	var squareCheckoutID *string
@@ -354,7 +369,12 @@ func CreateTillSale(w http.ResponseWriter, r *http.Request) {
 	desc := fmt.Sprintf("Gift Card %s (£%.2f)", req.Action, req.Amount)
 
 	var tillSaleID string
-	err = tx.QueryRow(ctx, `
+	if existingPendingID != "" {
+		// Reusing the pending sale row from a failed prior attempt — the sale
+		// was already inserted, so skip the insert and reuse its ID.
+		tillSaleID = existingPendingID
+	} else {
+		err = tx.QueryRow(ctx, `
 		INSERT INTO till_sales (
 			item_type, item_id, description, quantity, unit_price, total_amount,
 			payment_method, status, user_id, user_saved_card_id,
@@ -362,45 +382,49 @@ func CreateTillSale(w http.ResponseWriter, r *http.Request) {
 		) VALUES ($1, $2, $3, 1, $4, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, NOW(), NOW())
 		RETURNING id
 	`,
-		req.ItemType,
-		giftCardID,
-		desc,
-		req.Amount,
-		dbPaymentMethod,
-		saleStatus,
-		req.UserID,
-		req.UserSavedCardID,
-		squarePaymentID,
-		squareCheckoutID,
-		req.IdempotencyKey,
-		"Admin till sale: "+req.Action+" gift card",
-		adminID,
-	).Scan(&tillSaleID)
-	if err != nil {
-		log.Printf("Failed to insert till sale: %v", err)
-		http.Error(w, "internal server error", http.StatusInternalServerError)
-		return
-	}
+			req.ItemType,
+			giftCardID,
+			desc,
+			req.Amount,
+			dbPaymentMethod,
+			saleStatus,
+			req.UserID,
+			req.UserSavedCardID,
+			squarePaymentID,
+			squareCheckoutID,
+			req.IdempotencyKey,
+			"Admin till sale: "+req.Action+" gift card",
+			adminID,
+		).Scan(&tillSaleID)
+		if err != nil {
+			log.Printf("Failed to insert till sale: %v", err)
+			http.Error(w, "internal server error", http.StatusInternalServerError)
+			return
+		}
 
-	_, err = tx.Exec(ctx, `
+		_, err = tx.Exec(ctx, `
 		UPDATE gift_card_transactions SET reference_id = $1
 		WHERE gift_card_id = $2 AND reference_id IS NULL AND created_at > NOW() - INTERVAL '5 seconds'
 	`, tillSaleID, giftCardID)
-	if err != nil {
-		log.Printf("Failed to update gift_card_transactions reference: %v", err)
-		http.Error(w, "internal server error", http.StatusInternalServerError)
-		return
-	}
+		if err != nil {
+			log.Printf("Failed to update gift_card_transactions reference: %v", err)
+			http.Error(w, "internal server error", http.StatusInternalServerError)
+			return
+		}
 
-	if req.PaymentMethod != "on_the_house" && (saleStatus == "completed" || needsSquarePayment) {
-		vatCfg, vatErr := GetVATConfig(ctx, tx)
-		if vatErr == nil && vatCfg.IsVATRegistered && vatCfg.VoucherType == "SPV" {
-			if _, vatExecErr := tx.Exec(ctx, "SELECT apply_vat_to_till_sale($1, $2)", tillSaleID, vatCfg.DefaultVATRate); vatExecErr != nil {
-				log.Printf("Failed to apply VAT to till sale %s: %v", tillSaleID, vatExecErr)
+		if req.PaymentMethod != "on_the_house" && (saleStatus == "completed" || needsSquarePayment) {
+			vatCfg, vatErr := GetVATConfig(ctx, tx)
+			if vatErr == nil && vatCfg.IsVATRegistered && vatCfg.VoucherType == "SPV" {
+				if _, vatExecErr := tx.Exec(ctx, "SELECT apply_vat_to_till_sale($1, $2)", tillSaleID, vatCfg.DefaultVATRate); vatExecErr != nil {
+					log.Printf("Failed to apply VAT to till sale %s: %v", tillSaleID, vatExecErr)
+				}
 			}
 		}
 	}
 
+	// Commit the (possibly nested) transaction. In the pending-reuse path it is
+	// empty, but the commit releases the savepoint in the test harness so the
+	// deferred rollback does not undo the later status UPDATE.
 	if err := tx.Commit(ctx); err != nil {
 		log.Printf("Failed to commit till sale transaction: %v", err)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
@@ -436,9 +460,16 @@ func CreateTillSale(w http.ResponseWriter, r *http.Request) {
 			}
 			paymentResult, squareErr = SquareClient.CreatePayment(ctx, paymentReq)
 		} else if req.PaymentMethod == "online_square" {
-			cardOnFile, cardErr := SquareClient.CreateCardOnFileRaw(ctx, "till-"+giftCardID, req.CardNumber, req.CardExpMonth, req.CardExpYear, req.CardCVC)
+			// PCI-DSS: raw PANs are never accepted. The admin till must supply a
+			// Square Web Payments nonce (cnon:xxx), tokenized via the Cards API.
+			if req.CardToken == "" {
+				log.Printf("online_square till sale missing card_token for gift card %s", giftCardID)
+				http.Error(w, "card_token is required for online_square payment — use a Square Web Payments nonce", http.StatusBadRequest)
+				return
+			}
+			cardOnFile, cardErr := SquareClient.CreateCardOnFile(ctx, "till-"+giftCardID, req.CardToken)
 			if cardErr != nil {
-				log.Printf("Failed to tokenize ephemeral card: %v", cardErr)
+				log.Printf("Failed to tokenize card: %v", cardErr)
 				http.Error(w, "Card tokenization failed", http.StatusInternalServerError)
 				return
 			}
diff --git a/backend/handlers/payments/till_test.go b/backend/handlers/payments/till_test.go
index 3fcd2da..232209d 100644
--- a/backend/handlers/payments/till_test.go
+++ b/backend/handlers/payments/till_test.go
@@ -789,7 +789,7 @@ func TestCreateTillSale_SavedCardNoUserSavedCardID(t *testing.T) {
 	}
 }
 
-func TestCreateTillSale_OnlineSquareNoCardNumber(t *testing.T) {
+func TestCreateTillSale_OnlineSquareNoCardToken(t *testing.T) {
 	_, tx := testutils.SetupTestTx(t)
 
 	adminID, err := fixtures.CreateTestAdminUser(tx)
@@ -823,6 +823,128 @@ func TestCreateTillSale_OnlineSquareNoCardNumber(t *testing.T) {
 	}
 }
 
+func TestCreateTillSale_OnlineSquareWithToken(t *testing.T) {
+	_, tx := testutils.SetupTestTx(t)
+
+	adminID, err := fixtures.CreateTestAdminUser(tx)
+	if err != nil {
+		t.Fatalf("failed to create admin user: %v", err)
+	}
+
+	adminToken := jwt.GenerateTestToken(adminID, "admin")
+
+	reqBody := TillSaleRequest{
+		ItemType:      "gift_card",
+		Action:        "create",
+		Amount:        1000,
+		PaymentMethod: "online_square",
+		CardToken:     "cnon:visa",
+	}
+
+	bodyBytes, _ := json.Marshal(reqBody)
+	req := httptest.NewRequest("POST", "/api/admin/till/sale", bytes.NewReader(bodyBytes))
+	req.Header.Set("Authorization", "Bearer "+adminToken)
+	req.Header.Set("Content-Type", "application/json")
+	req = req.WithContext(db.ContextWithTx(req.Context(), tx.(pgx.Tx)))
+
+	w := httptest.NewRecorder()
+	r := chi.NewRouter()
+	r.Use(mw.RequireAuth)
+	r.Post("/api/admin/till/sale", CreateTillSale)
+	r.ServeHTTP(w, req)
+
+	if w.Code != http.StatusCreated && w.Code != http.StatusOK {
+		t.Errorf("expected 200/201, got %d. body: %s", w.Code, w.Body.String())
+	}
+}
+
+// TestCreateTillSale_PendingRetry_ReattemptsSquare verifies that a same-key
+// retry after a failed Square charge (sale stuck 'pending', gift card already
+// funded) re-attempts the charge and completes the sale — it must NOT return
+// the stale 'pending' status without re-charging (silent money loss).
+func TestCreateTillSale_PendingRetry_ReattemptsSquare(t *testing.T) {
+	t.Parallel()
+	ctx, tx := testutils.SetupTestTx(t)
+
+	adminID, err := fixtures.CreateTestAdminUser(tx)
+	if err != nil {
+		t.Fatalf("failed to create admin user: %v", err)
+	}
+	userID, err := fixtures.CreateTestUser(tx)
+	if err != nil {
+		t.Fatalf("failed to create user: %v", err)
+	}
+	adminToken := jwt.GenerateTestToken(adminID, "admin")
+
+	cardID, err := fixtures.CreateTestPaymentMethod(tx, userID, "sq_test_card_id", "VISA", "1234")
+	if err != nil {
+		t.Fatalf("failed to create saved card: %v", err)
+	}
+
+	// Seed a PENDING till_sale with the same key and a funded gift card —
+	// simulates a prior attempt where the Square charge failed after the DB
+	// transaction committed (card already funded).
+	key := "till-pending-retry-key"
+	var giftCardID string
+	err = tx.QueryRow(ctx, `
+		INSERT INTO gift_cards (total_funds_added, amount_remaining, created_by, is_inventory, voucher_type_at_purchase)
+		VALUES (50.00, 50.00, $1, FALSE, 'SPV')
+		RETURNING id
+	`, adminID).Scan(&giftCardID)
+	if err != nil {
+		t.Fatalf("failed to create gift card: %v", err)
+	}
+	_, err = tx.Exec(ctx, `
+		INSERT INTO till_sales (item_type, item_id, description, quantity, unit_price, total_amount,
+			payment_method, status, user_id, user_saved_card_id, idempotency_key, created_by, created_at, updated_at)
+		VALUES ('gift_card', $1, 'Gift Card create', 1, 50.00, 50.00, 'online_square', 'pending',
+			$2, $3, $4, $5, NOW(), NOW())
+	`, giftCardID, userID, cardID, key, adminID)
+	if err != nil {
+		t.Fatalf("failed to seed pending till sale: %v", err)
+	}
+
+	reqBody := TillSaleRequest{
+		ItemType:        "gift_card",
+		Action:          "create",
+		Amount:          50.00,
+		PaymentMethod:   "saved_card",
+		UserSavedCardID: &cardID,
+		UserID:          &userID,
+		IdempotencyKey:  key,
+	}
+
+	bodyBytes, _ := json.Marshal(reqBody)
+	req := httptest.NewRequest("POST", "/api/admin/till/sale", bytes.NewReader(bodyBytes))
+	req.Header.Set("Authorization", "Bearer "+adminToken)
+	req.Header.Set("Content-Type", "application/json")
+	req = req.WithContext(db.ContextWithTx(req.Context(), tx.(pgx.Tx)))
+
+	w := httptest.NewRecorder()
+	r := chi.NewRouter()
+	r.Use(mw.RequireAuth)
+	r.Post("/api/admin/till/sale", CreateTillSale)
+	r.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK && w.Code != http.StatusCreated {
+		t.Fatalf("expected 200/201, got %d. body: %s", w.Code, w.Body.String())
+	}
+
+	// The sale must now be 'completed' (Square re-attempted and succeeded).
+	var saleStatus string
+	var saleCount int
+	err = tx.QueryRow(ctx, `SELECT COUNT(*), MAX(status) FROM till_sales WHERE idempotency_key = $1`, key).Scan(&saleCount, &saleStatus)
+	if err != nil {
+		t.Fatalf("failed to query till sale: %v", err)
+	}
+	if saleCount != 1 {
+		t.Errorf("expected 1 till sale (reuse, not duplicate), got %d", saleCount)
+	}
+	if saleStatus != "completed" {
+		t.Errorf("expected pending sale to be completed after retry, got %s", saleStatus)
+	}
+}
+
 func TestCreateTillSale_CreateCash(t *testing.T) {
 	ctx, tx := testutils.SetupTestTx(t)
 
diff --git a/backend/internal/square/square.go b/backend/internal/square/square.go
index d5fd15c..95db980 100644
--- a/backend/internal/square/square.go
+++ b/backend/internal/square/square.go
@@ -2,10 +2,7 @@
 
 package square
 
-import (
-	"context"
-	"fmt"
-)
+import "context"
 
 var Client SquareClient
 
@@ -39,10 +36,6 @@ func (p *ProdClient) CreateCardOnFile(ctx context.Context, userID, cardToken str
 	return createCardOnFileHTTP(ctx, userID, cardToken)
 }
 
-func (p *ProdClient) CreateCardOnFileRaw(ctx context.Context, userID, cardNumber string, expMonth, expYear int, cvc string) (*CardOnFile, error) {
-	return nil, fmt.Errorf("square: raw card number input is not supported in production — use CreateCardOnFile with a card nonce")
-}
-
 func (p *ProdClient) GetCardsOnFile(ctx context.Context, userID string) ([]CardOnFile, error) {
 	return getCardsOnFileHTTP(ctx, userID)
 }
diff --git a/backend/internal/square/square_dev.go b/backend/internal/square/square_dev.go
index 757f30a..8f78688 100644
--- a/backend/internal/square/square_dev.go
+++ b/backend/internal/square/square_dev.go
@@ -52,9 +52,6 @@ func (d *devProdClient) RefundPayment(ctx context.Context, req RefundPaymentReq)
 func (d *devProdClient) CreateCardOnFile(ctx context.Context, userID, cardToken string) (*CardOnFile, error) {
 	return createCardOnFileHTTP(ctx, userID, cardToken)
 }
-func (d *devProdClient) CreateCardOnFileRaw(ctx context.Context, userID, cardNumber string, expMonth, expYear int, cvc string) (*CardOnFile, error) {
-	return nil, fmt.Errorf("square: raw card number input is not supported in production — use CreateCardOnFile with a card nonce")
-}
 func (d *devProdClient) GetCardsOnFile(ctx context.Context, userID string) ([]CardOnFile, error) {
 	return getCardsOnFileHTTP(ctx, userID)
 }
@@ -373,13 +370,6 @@ func (m *MockClient) CreateCardOnFile(ctx context.Context, userID, cardToken str
 	return card, nil
 }
 
-func (m *MockClient) CreateCardOnFileRaw(ctx context.Context, userID, cardNumber string, expMonth, expYear int, cvc string) (*CardOnFile, error) {
-	// PCI-DSS parity with production: raw card numbers are never accepted.
-	// The mock must behave identically to the ProdClient so dev testing does
-	// not mask a production failure.
-	return nil, fmt.Errorf("square: raw card number input is not supported in production — use CreateCardOnFile with a card nonce")
-}
-
 func (m *MockClient) GetCardsOnFile(ctx context.Context, userID string) ([]CardOnFile, error) {
 	log.Printf("[SQUARE-MOCK] GetCardsOnFile: user=%s", userID)
 
diff --git a/backend/internal/square/square_dev_test.go b/backend/internal/square/square_dev_test.go
index 151868e..0671cc2 100644
--- a/backend/internal/square/square_dev_test.go
+++ b/backend/internal/square/square_dev_test.go
@@ -237,9 +237,9 @@ func TestDevClient_GetCheckout_NotFound(t *testing.T) {
 	require.Error(t, err)
 }
 
-func TestDevClient_CreateCardOnFileRaw_Rejected_ProdParity(t *testing.T) {
-	// PCI-DSS parity: the mock must reject raw PANs exactly like the
-	// ProdClient, so dev testing cannot mask a production failure.
+func TestDevClient_CreateCardOnFile_RejectsRawPAN(t *testing.T) {
+	// PCI-DSS parity: CreateCardOnFile accepts only token-like source_ids
+	// (cnon:xxx / ccof:xxx). Raw PANs are rejected exactly like real Square.
 	client := NewDevClient().(*MockClient)
 	ctx := context.Background()
 
@@ -251,16 +251,15 @@ func TestDevClient_CreateCardOnFileRaw_Rejected_ProdParity(t *testing.T) {
 		{"mastercard", "5555555555554444"},
 		{"amex", "378282246310005"},
 		{"discover", "6011111111111117"},
-		{"unknown brand", "9999999999999999"},
 		{"too short", "123"},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			card, err := client.CreateCardOnFileRaw(ctx, "user-raw-"+tt.name, tt.cardNumber, 12, 2030, "123")
+			card, err := client.CreateCardOnFile(ctx, "user-raw-"+tt.name, tt.cardNumber)
 			require.Error(t, err, "raw PAN must be rejected for production parity")
 			assert.Nil(t, card)
-			assert.Contains(t, err.Error(), "raw card number input is not supported")
+			assert.Contains(t, err.Error(), "invalid source_id")
 		})
 	}
 }
@@ -372,6 +371,37 @@ func TestDevClient_CreatePayment_WithTipMoney(t *testing.T) {
 	assert.Equal(t, int64(1000), result.TipAmount)
 }
 
+func TestDevClient_CreatePayment_DedupsOnIdempotencyKey(t *testing.T) {
+	// Real Square dedups on idempotency key: a same-key retry returns the
+	// original payment. The mock must mirror this or dev/testing diverges
+	// from production (and the pending-retry logic can't be exercised).
+	client := NewDevClient().(*MockClient)
+	ctx := context.Background()
+
+	req := CreatePaymentReq{
+		Amount:         5000,
+		Currency:       "GBP",
+		SourceID:       "cnon:test-card",
+		IdempotencyKey: "dedup-key-1",
+		ReferenceID:    "booking-dedup",
+	}
+
+	first, err := client.CreatePayment(ctx, req)
+	require.NoError(t, err)
+	require.NotEmpty(t, first.ID)
+
+	second, err := client.CreatePayment(ctx, req)
+	require.NoError(t, err)
+	assert.Equal(t, first.ID, second.ID, "same-key retry must return the original payment, not a new one")
+
+	// Total stored payments for this key must be one (deduped).
+	client.mu.RLock()
+	byKey := client.paymentByKey["dedup-key-1"]
+	client.mu.RUnlock()
+	assert.NotNil(t, byKey)
+	assert.Equal(t, first.ID, byKey.ID)
+}
+
 func TestDevClient_CreatePayment_AutocompleteFalse(t *testing.T) {
 	client := NewDevClient().(*MockClient)
 	ctx := context.Background()
@@ -426,41 +456,6 @@ func TestDevClient_CreateCardOnFile_WithNewFields(t *testing.T) {
 	assert.NotEmpty(t, card.CreatedAt)
 }
 
-func TestDevClient_CreateCardOnFileRaw_WithBrandDetection(t *testing.T) {
-	client := NewDevClient().(*MockClient)
-	ctx := context.Background()
-	userID := "user-raw-brand-detect"
-
-	card, err := client.CreateCardOnFileRaw(ctx, userID, "4111111111111111", 12, 2030, "123")
-	require.Error(t, err, "raw PAN must be rejected for production parity")
-	assert.Nil(t, card)
-}
-
-func TestDevClient_CreateCardOnFile_RejectsRawPAN(t *testing.T) {
-	client := NewDevClient().(*MockClient)
-	ctx := context.Background()
-
-	tests := []struct {
-		name    string
-		cardNum string
-	}{
-		{"visa formatted", "4111 1111 1111 1111"},
-		{"visa raw", "4111111111111111"},
-		{"mastercard", "5500 0000 0000 0004"},
-		{"amex", "3400 0000 0000 009"},
-		{"discover", "6011 0000 0000 0004"},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			userID := fmt.Sprintf("user-raw-card-%s", tt.name)
-			card, err := client.CreateCardOnFile(ctx, userID, tt.cardNum)
-			require.Error(t, err, "raw PAN must be rejected for production parity")
-			assert.Nil(t, card)
-		})
-	}
-}
-
 func TestDevClient_DeleteCardOnFile_SoftDelete(t *testing.T) {
 	client := NewDevClient().(*MockClient)
 	ctx := context.Background()
@@ -478,15 +473,6 @@ func TestDevClient_DeleteCardOnFile_SoftDelete(t *testing.T) {
 	assert.False(t, cards[0].Enabled)
 }
 
-func TestDevClient_CreateCardOnFileRaw_TooShort(t *testing.T) {
-	client := NewDevClient().(*MockClient)
-	ctx := context.Background()
-
-	_, err := client.CreateCardOnFileRaw(ctx, "user-too-short", "123", 12, 2030, "999")
-	require.Error(t, err)
-	assert.Contains(t, err.Error(), "raw card number input is not supported")
-}
-
 func TestDevClient_GetCardsOnFile_Empty(t *testing.T) {
 	client := NewDevClient().(*MockClient)
 	ctx := context.Background()
diff --git a/backend/internal/square/types.go b/backend/internal/square/types.go
index 1e868ce..572fe3f 100644
--- a/backend/internal/square/types.go
+++ b/backend/internal/square/types.go
@@ -137,7 +137,6 @@ type SquareClient interface {
 	GetCheckout(ctx context.Context, checkoutID string) (*PaymentResult, error)
 	RefundPayment(ctx context.Context, req RefundPaymentReq) (*RefundResult, error)
 	CreateCardOnFile(ctx context.Context, userID, cardToken string) (*CardOnFile, error)
-	CreateCardOnFileRaw(ctx context.Context, userID, cardNumber string, expMonth, expYear int, cvc string) (*CardOnFile, error)
 	GetCardsOnFile(ctx context.Context, userID string) ([]CardOnFile, error)
 	DeleteCardOnFile(ctx context.Context, cardID string) error
 }
diff --git a/frontend/src/lib/components/booking/BookingFlow.svelte b/frontend/src/lib/components/booking/BookingFlow.svelte
index c1a020c..a94dac4 100644
--- a/frontend/src/lib/components/booking/BookingFlow.svelte
+++ b/frontend/src/lib/components/booking/BookingFlow.svelte
@@ -136,13 +136,22 @@
 	const cardError = $derived(
 		cardNumberTouched && !isValidLuhn(newCardNumber) && newCardNumber.length > 0
 			? 'Invalid card number'
-			: cardExpiryTouched && expiryParts !== null && (() => { const em = expiryParts.year * 12 + expiryParts.month; const now2 = new SvelteDate(); const cm = now2.getFullYear() * 12 + now2.getMonth() + 1; return em < cm; })()
+			: cardExpiryTouched &&
+				  expiryParts !== null &&
+				  (() => {
+						const em = expiryParts.year * 12 + expiryParts.month;
+						const now2 = new SvelteDate();
+						const cm = now2.getFullYear() * 12 + now2.getMonth() + 1;
+						return em < cm;
+				  })()
 				? 'This card has expired'
 				: cardExpiryTouched && !/^\d{2}\/\d{2}$/.test(newCardExpiry) && newCardExpiry.length > 0
 					? 'Enter expiry as MM/YY'
 					: cardCVCTouched && newCardCVC.length < 3 && newCardCVC.length > 0
 						? 'Enter your CVC number'
-						: isValidLuhn(newCardNumber) && /^\d{2}\/\d{2}$/.test(newCardExpiry) && newCardCVC.length >= 3
+						: isValidLuhn(newCardNumber) &&
+							  /^\d{2}\/\d{2}$/.test(newCardExpiry) &&
+							  newCardCVC.length >= 3
 							? null
 							: newCardNumber.length === 0 && newCardExpiry.length === 0 && newCardCVC.length === 0
 								? null
@@ -345,10 +354,23 @@
 			const bookingId = confirmedBooking.id;
 			const amountCents = Math.round(amount * 100);
 
+			// Cache the idempotency key per amount+card so a lost-response retry
+			// reuses it (backend dedups) instead of double-charging.
+			const cardKey = selectedPaymentMethod ?? newCardNumber.replace(/\s/g, '') ?? '';
+			if (
+				!depositIdempotencyKey ||
+				depositKeyedAmount !== amountCents ||
+				depositKeyedCard !== cardKey
+			) {
+				depositIdempotencyKey = generateUUID();
+				depositKeyedAmount = amountCents;
+				depositKeyedCard = cardKey;
+			}
+
 			const body: Record<string, unknown> = {
 				payment_type: 'deposit',
 				amount: amountCents,
-				idempotency_key: generateUUID()
+				idempotency_key: depositIdempotencyKey
 			};
 
 			if (selectedPaymentMethod) {
@@ -373,6 +395,9 @@
 
 			if (response.ok) {
 				depositPaid = true;
+				depositIdempotencyKey = '';
+				depositKeyedAmount = 0;
+				depositKeyedCard = '';
 				// Immutable update — avoid mutating the existing object so
 				// concurrent renders (e.g. a stale fetch) can't observe partial
 				// state. (See audit: HIGH issue #3 — confirmedBooking mutated
@@ -400,6 +425,13 @@
 
 	let paymentAttempted = $state(false);
 
+	// Cached idempotency key per deposit attempt (amount + card): reused on
+	// retry so a lost-response retry dedups instead of double-charging,
+	// regenerated when the amount or card changes. Matches the tip-flow pattern.
+	let depositIdempotencyKey = $state('');
+	let depositKeyedAmount = $state(0);
+	let depositKeyedCard = $state('');
+
 	function formatCardExpiry(month: number, year: number): string {
 		return `${String(month).padStart(2, '0')}/${year.toString().slice(-2)}`;
 	}
diff --git a/frontend/src/lib/components/payments/UserPaymentModal.svelte b/frontend/src/lib/components/payments/UserPaymentModal.svelte
index 79eeb80..abc9ed0 100644
--- a/frontend/src/lib/components/payments/UserPaymentModal.svelte
+++ b/frontend/src/lib/components/payments/UserPaymentModal.svelte
@@ -29,6 +29,14 @@
 
 	let status = $state<PaymentStatus>('idle');
 	let error = $state<string | null>(null);
+
+	// Cached idempotency key per payment attempt (amount + type + card): reused
+	// on retry so a lost-response retry dedups instead of double-charging,
+	// regenerated when any of those change. Matches the tip-flow pattern.
+	let payIdempotencyKey = $state('');
+	let payKeyedAmount = $state(0);
+	let payKeyedType = $state('');
+	let payKeyedCard = $state('');
 	let paymentResult = $state<{
 		id: string;
 		amount: number;
@@ -354,7 +362,20 @@
 			return;
 		}
 
-		const idempotencyKey = generateIdempotencyKey();
+		// Cache the idempotency key per amount+type+card so a lost-response
+		// retry reuses it (backend dedups) instead of double-charging.
+		const cardKey = cardId ?? newCardToken ?? '';
+		if (
+			!payIdempotencyKey ||
+			payKeyedAmount !== amountCents ||
+			payKeyedType !== paymentType ||
+			payKeyedCard !== cardKey
+		) {
+			payIdempotencyKey = generateIdempotencyKey();
+			payKeyedAmount = amountCents;
+			payKeyedType = paymentType;
+			payKeyedCard = cardKey;
+		}
 
 		try {
 			const response = await apiFetch(`/api/bookings/${booking.id}/payment`, {
@@ -366,7 +387,7 @@
 					card_id: cardId,
 					new_card_token: newCardToken,
 					save_card: saveCard,
-					idempotency_key: idempotencyKey
+					idempotency_key: payIdempotencyKey
 				})
 			});
 
@@ -378,6 +399,10 @@
 			const data = await response.json();
 			// Payment is synchronous (completed immediately)
 			status = 'success';
+			payIdempotencyKey = '';
+			payKeyedAmount = 0;
+			payKeyedType = '';
+			payKeyedCard = '';
 			paymentResult = {
 				id: data.id,
 				amount: data.amount,
diff --git a/frontend/src/routes/account/+page.svelte b/frontend/src/routes/account/+page.svelte
index f24169a..879512a 100644
--- a/frontend/src/routes/account/+page.svelte
+++ b/frontend/src/routes/account/+page.svelte
@@ -180,6 +180,13 @@
 	let buyingGiftCard = $state(false);
 	let purchaseResultCode = $state<string | null>(null);
 
+	// Cached idempotency key: generated once per purchase attempt, reused on
+	// retry (so a lost-response retry dedups instead of double-charging),
+	// cleared on success. Reset when the amount or payment method changes.
+	let buyIdempotencyKey = $state('');
+	let buyKeyedAmount = $state(0);
+	let buyKeyedCard = $state('');
+
 	$effect(() => {
 		// Auto-select the default saved card only once, when cards first load.
 		// Do NOT re-select when the user explicitly chooses "Use a new card"
@@ -337,7 +344,15 @@
 				return;
 			}
 
-			const idempotencyKey = generateIdempotencyKey();
+			// Cache the idempotency key per amount+card so a lost-response retry
+			// reuses the same key (backend dedups) instead of double-charging.
+			// Regenerate when the amount or card changes.
+			const cardKey = cardId ?? newCardToken ?? '';
+			if (!buyIdempotencyKey || buyKeyedAmount !== buyAmount || buyKeyedCard !== cardKey) {
+				buyIdempotencyKey = generateIdempotencyKey();
+				buyKeyedAmount = buyAmount;
+				buyKeyedCard = cardKey;
+			}
 
 			const res = await apiFetch('/api/user/giftcards/buy', {
 				method: 'POST',
@@ -349,7 +364,7 @@
 					card_id: cardId,
 					new_card_token: newCardToken,
 					save_card: saveCard,
-					idempotency_key: idempotencyKey
+					idempotency_key: buyIdempotencyKey
 				})
 			});
 
@@ -360,6 +375,9 @@
 				buyNewCardNumber = '';
 				buyNewCardExpiry = '';
 				buyNewCardCVC = '';
+				buyIdempotencyKey = '';
+				buyKeyedAmount = 0;
+				buyKeyedCard = '';
 				await fetchGiftCardBalance();
 				if (buySelectedCard === '') {
 					await savedCardsStore.fetch();
diff --git a/init-scripts/init-script.sql b/init-scripts/init-script.sql
index d1788f3..fedaaf0 100644
--- a/init-scripts/init-script.sql
+++ b/init-scripts/init-script.sql
@@ -1989,6 +1989,7 @@ CREATE TABLE refunds (
     square_refund_id TEXT,
     status payment_status NOT NULL DEFAULT 'pending',
     reason TEXT NOT NULL,
+    idempotency_key VARCHAR(64) UNIQUE,
     created_by CHAR(12) REFERENCES users(id) ON DELETE SET NULL,
     created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
 );