> ## Documentation Index
> Fetch the complete documentation index at: https://docs.meum.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Exchange rate handling

> FX conversion and quote locking behavior.

When an invoice currency is not USD, Meum converts the amount to USD for platform validation and checkout quoting.

## Quote locking

After a customer selects a payment token at checkout:

1. A checkout quote is generated with a deposit address and expected crypto amount
2. The quote has a **rate lock period** configured by platform settings
3. If the customer pays within the lock window, the quoted rate applies

<Info>
  Exact rate lock duration is controlled by platform configuration (`checkoutQuoteGraceMs`, `paymentRateLockedMs`). Requires verification in your environment if you need precise timing for support SLAs.
</Info>

## Expected vs received amount

After payment detection:

* `expected_amount` — amount required at quote time
* `received_amount` / `paid_amount` — actual on-chain amount received
* `difference_amount` — delta; used to determine `paid` vs `underpaid`

## Related pages

* [Underpayment and overpayment](/payments/underpayment-and-overpayment)
* [Transaction confirmations](/payments/transaction-confirmations)