What's a duplicate slip, and how do you catch one?

Short answer: a duplicate slip is a slip that already paid for something, sent again to pay a new order. You can't tell from the picture, because it's a real slip. You catch it by checking the transaction reference and the transfer time against money that really arrived.

Where duplicate slips come from

• The same buyer resends an old slip, sometimes by mistake
• A forwarded slip: someone else's transfer, to another shop, passed on to yours
• One slip for two orders: the buyer ordered twice but sends the same slip for both bills

How to check by hand

1. Look at the transaction reference on the slip and search the ones you've used. Same reference = same slip.
2. Look at the transfer time. A transfer made before you sent the bill can't be paying it.
3. Look at the receiving account. It must be your shop's PromptPay.
4. Open your banking app and confirm the money arrived at that time and amount.

A polite reply (Thai):

สลิปใบนี้ร้านได้รับไปแล้วกับออเดอร์ก่อนหน้านะคะ 🙏 รบกวนส่งสลิปของออเดอร์นี้ให้อีกครั้งได้ไหมคะ ถ้าโอนรวมไว้ บอกร้านได้เลยค่ะ เดี๋ยวช่วยเช็คให้

"We already received this slip for an earlier order 🙏 Could you send the slip for this order? If you paid both together, just tell us and we'll check."

How Nava helps

Nava checks every slip against bank data and remembers every slip the shop has used. A slip can't be used again for another order in the shop; it shows "this slip has already been used". The slip must be paid into this shop's PromptPay and match the bill to the satang, so a slip forwarded from a transfer to another shop doesn't pass. Nava is in a private pilot and opens to everyone in February 2027.

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