What an invoice does
What it contains
Six fields, and each solves a specific problem.
The fiat amount
What is actually owed, denominated in the currency the business prices in.
The crypto amount
The fiat amount converted at the current rate.
The address
Generated fresh for this invoice, which is how the payment gets matched to the order without anybody comparing anything.
The network
Fixed, because the same asset on another chain will not arrive.
The expiry
A countdown, commonly ten to twenty minutes.
A reference
The order number, held by the provider rather than sent with the transfer.
How rate locking works
This is the part an invoice exists for.
Between quoting a price and receiving a payment, the coin’s price moves. Without a lock, a merchant billing 100 dollars might receive 97 or 104 worth, and neither outcome is acceptable in accounting terms.
The invoice fixes the exchange rate for its window. Pay inside it and the business receives the quoted fiat value. The provider absorbs the movement during that period, which is one of the things a processing fee pays for.
The window is short because the risk grows with time. A twenty-minute lock is manageable; a day is not, which is why invoices expire rather than staying open.
When it goes wrong
What happens on expiry
The invoice closes and the address stops being watched for that order.
Pay late and the transfer still confirms on the network, because nothing on-chain knows about the expiry. The payment arrives somewhere real and is not attached to an order. ##### How a late payment gets matched
Resolution is manual: provide the transaction hash, the provider matches it, and the order is credited at whatever rate the agreement specifies.
This is a normal support case rather than a lost payment, and it is worth telling customers about, since a visible countdown prevents most of it.
Partial and excess payments
Both happen, mostly for one reason.
Underpayment usually means the sender’s wallet deducted the network fee from the amount instead of adding it. The invoice stays unpaid with the shortfall recorded, and the merchant either requests the difference or credits partially.
Overpayment is credited or refunded depending on the provider’s rules and the merchant’s settings.
Invoices between companies
Invoices for business-to-business billing
A different use, and the requirements change.
An invoice between companies needs legal details: both parties named, registration numbers, a description of what is supplied, tax treatment where applicable. That document is issued in fiat as normal, and the crypto payment settles it.
The accounting record needs the fiat equivalent at the moment of receipt rather than at the moment of invoicing, because that is the figure bookkeeping works with. A payment gateway stores this against each payment, along with the amount, coin, network and hash, and the setup guide covers how it reaches your records.