Exact-Amount Payment Matching

Overview

What it means and why it exists

Exact-amount payment matching identifies an expected customer payment by comparing the received asset amount with a precisely requested amount, often alongside other information such as address and time.

How it works

The processor records an invoice amount in the token's smallest units and checks observed transfers for an equal amount on the correct chain and asset. Some systems intentionally assign distinctive fractional amounts to orders sharing a receiving address. The match is only a candidate until transaction success, recipient and confirmation policies are verified.

Technical details worth understanding

Precision is central: USDC commonly uses six decimals on Ethereum, while other assets use different unit scales. An amount displayed as 2.50 may have a different integer representation across assets. The payer's network fee is usually separate and should not be incorrectly deducted from the merchant's received amount.

What can go wrong

Two customers can independently send the same amount at overlapping times, and a payer may round or split a payment. Fee-on-transfer tokens can make the received amount different from the entered amount. Never treat an exact numeric match alone as proof of order ownership.

Practical checks

Store amounts as integers in token base units to avoid floating-point errors. Use collision detection if several invoices can request the same exact value to a shared address during overlapping windows. Verify that gas fees, token transfer fees and network rounding have not silently changed the actual amount received.

Related concepts

Crypto Invoice, Crypto Payment Status, Crypto Checkout.

Further reading

OxaPay — Developer Documentation.