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

# useNFCMerchant

> React hook for creating NFC payment requests as a merchant.

`useNFCMerchant` manages the merchant side of the payment flow: calling the backend to create a payment request and providing state for the result.

## Import

```ts theme={null}
import { useNFCMerchant } from '@taprails/tap-to-pay';
```

## Usage

```tsx theme={null}
const {
  createPaymentRequest,
  isCreating,
  isSuccess,
  paymentRequest,
  error,
  reset,
} = useNFCMerchant();
```

## Return Value

<ResponseField name="createPaymentRequest" type="(params) => Promise<PaymentRequest | null>">
  Creates a payment request on the TapRails backend. Returns a `PaymentRequest` on success, or `null` if an error occurs (check the `error` state).
</ResponseField>

<ResponseField name="isCreating" type="boolean">
  `true` while the backend request is in-flight.
</ResponseField>

<ResponseField name="isSuccess" type="boolean">
  `true` after a payment request has been successfully created.
</ResponseField>

<ResponseField name="paymentRequest" type="PaymentRequest | null">
  The most recently created payment request, or `null` before any request is made.
</ResponseField>

<ResponseField name="error" type="Error | null">
  Error from the most recent `createPaymentRequest` call, or `null` on success.
</ResponseField>

<ResponseField name="reset" type="() => void">
  Clears all state — useful when starting a new payment flow.
</ResponseField>

***

## createPaymentRequest params

<ParamField path="amount" type="string" required>
  Payment amount in USDC as a decimal string — e.g., `"25.00"`. Do not pass a number.
</ParamField>

<ParamField path="merchantId" type="string">
  Merchant identifier. Falls back to `merchantId` from `ContactlessCryptoSDK.initialize()` if omitted.
</ParamField>

***

## Example

```tsx theme={null}
import { useNFCMerchant, writeSignedInvoice } from '@taprails/tap-to-pay';
import { useState } from 'react';

export function MerchantPOS() {
  const [exchanged, setExchanged] = useState(false);
  const { createPaymentRequest, isCreating, paymentRequest, error, reset } = useNFCMerchant();

  const startPayment = async () => {
    const request = await createPaymentRequest({ amount: '50.00' });
    if (!request) return;

    // Begin HCE emulation so the customer can tap
    await writeSignedInvoice(
      {
        id: request.paymentId,
        merchantAddress: request.merchantWallet,
        amount: Math.round(50 * 1_000_000), // to µUSDC
        expiresAt: request.expiresAt!,
      },
      setExchanged
    );
  };

  if (isCreating) return <Text>Creating payment…</Text>;
  if (exchanged) return <Text>Customer tapped — processing…</Text>;

  return (
    <>
      {error && <Text style={{ color: 'red' }}>{error.message}</Text>}
      <Button title="Charge $50.00" onPress={startPayment} />
    </>
  );
}
```

<Note>
  After `createPaymentRequest` succeeds, call `writeSignedInvoice` to start NFC emulation (HCE). The hook itself does not initiate NFC — it only handles backend communication.
</Note>