> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cryptoprocessing.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Payment requests
export const Expired = () => Expired;
With payment requests, you can let your customers make one-time payments in the cryptocurrency of their choice.
* **Your customer** sees a convenient webpage that guides them through the payment process.
* **You** receive funds in the currency you requested, regardless of the customer's payment currency.
* **CryptoProcessing** takes care of conversion and issues automatic refunds for underpayments and overpayments.
When creating a payment request, you control its behavior by choosing the [currency](#currency-selection) and the [lifespan](#lifespan-and-rate-lock).
The funds received via a payment request may be sent back via a [refund](/payment-requests/refunds), initiated either automatically or manually by you.
## Currency selection
When creating a payment request, you specify the **expected currency** — the fiat or cryptocurrency you want to receive. The **payment currency** is chosen at checkout by your customer from the allowed currencies (you can [customize the selection](/payment-requests/currencies)), or it can be set explicitly via the `payment_currency` parameter in the [API request](/api-reference/endpoints/payments).
If the customer pays in a currency that's different from the expected currency, CryptoProcessing converts the funds automatically, so you still receive the exact amount and currency you requested. The [conversion rate is locked](#lifespan-and-rate-lock) for up to 1 hour while awaiting a transaction for the customer.
The total amount to pay never changes after the rate lock. It may include the processing fee for the selected currency if you [pass the processing fee to the customer](/payment-requests/fees#passing-the-processing-fee-to-your-customer).
[Refunds](/payment-requests/refunds) are issued in the same currency the customer used to pay the request.
## Lifespan and rate lock
There are two time constraints applicable to a payment request.
* The **lifespan** is set by you when you create a payment request. The customer's transaction must be both created and confirmed within this lifespan, or the payment request expires.
* The **rate lock** is applied if the customer chooses a payment currency that differs from the expected currency. CryptoProcessing locks the conversion rate for up to **1 hour** (or less, if the lifespan ends sooner). The customer's transaction must be both created and confirmed within the rate lock period, or the payment request expires.
When the payment request has less than 1 hour left before expiration, the customer sees a countdown timer on the webpage.
## Further reading
Learn how to integrate the payment requests flow into your site
Walk through all scenarios to make sure your integration works correctly
API endpoint
API callback
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