Send the exact crypto amount — fee on top, not from the quote

Every failed crypto payment we see falls into one of two buckets. The bigger bucket, by a large margin, is not "wrong network" or "wrong address". It is "right address, right network, wrong amount". Usually off by cents. Occasionally off by a whole coin.

This is what actually happens, why, and how to stop it happening to you.

Why the exact amount matters

A fixed-price crypto checkout is doing one job: watching a specific address for a specific value in a specific window. When the value lands, the order flips to paid and the QR code goes out.

If the value that lands is even a fraction under the quote, the merchant's system has two problems. It does not know whether more is coming, and it does not know whether to refund what did arrive. So it waits, usually for a human. On a live-support day that human is minutes away. Overnight, it can be hours.

Overpayment is inconvenient — the merchant will refund the difference. Underpayment is slow, because someone has to decide what to do with a half-paid order.

Fee on top vs fee from amount

Every crypto transaction has two numbers: the amount you send and the network fee. Wallets disagree, quietly, about which of those comes out of what.

Fee on top. You type 12.40. The wallet debits 12.40 + fee. The recipient receives exactly 12.40. This is what a checkout expects.

Fee from amount. You type 12.40. The wallet debits 12.40 total, splitting it between the recipient and the network. The recipient receives 12.40 minus the fee — perhaps 12.37 on Tron, perhaps 11.90 on Ethereum. This is what a checkout does not expect.

Both behaviours are legitimate. Both are ways someone might reasonably interpret "send 12.40". The problem is the label almost never says which one you are looking at.

Do not press Max

Every crypto wallet has a Max button. It fills the amount field with the biggest number that lets the transaction still succeed. On a self-transfer, that is exactly what you want.

On a merchant payment, Max is a footgun. It ignores the merchant's quote entirely. If your balance is 43 USDT and the quote is 12.40, Max will send 43 (minus fees). You have just overpaid a $12 order by $30 and the refund conversation starts now.

The fix is boring: type the number the merchant quoted. Copy-paste it. Verify the last two digits.

What to actually do at checkout

1. 1

   Copy the amount from the checkout, not from memory

   The quote will look like 12.4008 or similar, out to more decimals than you would type by hand. Copy the whole thing. Wallets accept the extra precision.

2. 2

   Confirm the wallet is fee-on-top

   If you did the self-transfer test, you already know. If you did not, look at the confirmation screen: the wallet almost always shows a You send number and a Recipient receives number. They should be equal (fee-on-top) — or if they are not, adjust the You send number upward until Recipient receives matches the merchant quote.

3. 3

   Send, and copy the transaction hash before you close the wallet

   Do not leave the wallet until you have the hash on the clipboard or in your email. It is the only reference that lets support match your transaction to your order if anything goes sideways.

4. 4

   Do not send a second transaction because the first one 'looked stuck'

   Fast chains confirm in seconds. Slow chains take a minute. If the checkout page has not updated after two minutes, refresh the page — do not resend. A second transfer creates two rows to reconcile instead of one, and doubles the time to a fix.

The rare case: you underpaid anyway

It happens. Wallet defaults change, exchange rates shift a decimal, or you fat-fingered the amount.

If the checkout page shows the order as underpaid or waiting, do exactly this:

• Do not send another transaction from a different wallet. Support can match one address to one order. Two addresses to one order is a manual process.
• Copy the transaction hash and the order ID and open a support message.
• Wait. Most merchants close the gap within a working day by either topping up an internal account or refunding you and reissuing the order.

The recovery is boring and it works. The failure mode is people getting impatient and firing a second transaction before the first is reconciled, at which point everything takes twice as long.

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