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

# Sponsor USDC Payments

> Enable zero-gas USDC transfers for your users.

Your user wants to send USDC to a friend. They do not have XLM, and they should not need it to move their digital dollars. This guide shows you how to build, sign, and sponsor a USDC payment using Grat. You can see this in action on our [Live Demo](https://grat-usdc-transfer-web.vercel.app/).

### Prerequisites

* A running Grat relay (see the [Quickstart](/quickstart)).
* The Grat TypeScript SDK installed.

<Steps>
  <Step title="Initialize the SDK">
    Connect to your local relay.

    ```typescript theme={null}
    import { Grat } from '@grat-official-sdk/sdk';
    const grat = Grat.testnet();
    ```
  </Step>

  <Step title="Establish a USDC Trustline">
    Before a user can receive USDC on Stellar, they must establish a trustline. You can sponsor this setup transaction as well.

    ```typescript theme={null}
    import { Asset, TransactionBuilder, Networks, Operation } from '@stellar/stellar-sdk';

    const usdc = new Asset("USDC", "GBBD67IFX53O3S6ZDHAYQ4M6Z67G4C3K6G5Y6S6TORYS6A7XNQLS6");

    const trustTx = new TransactionBuilder(
      { publicKey: userKp.publicKey(), sequence: "123" },
      { fee: "100", networkPassphrase: Networks.TESTNET }
    )
    .addOperation(Operation.changeTrust({ asset: usdc }))
    .setTimeout(30)
    .build();

    trustTx.sign(userKp);
    await grat.sponsor(trustTx);
    ```
  </Step>

  <Step title="Build a USDC Payment">
    Build a standard payment transaction. Note that you don't need to worry about Alice having XLM for the fee, as Grat will cover it.

    ```typescript theme={null}
    const paymentTx = new TransactionBuilder(
      { publicKey: senderKp.publicKey(), sequence: "124" },
      { fee: "100", networkPassphrase: Networks.TESTNET }
    )
    .addOperation(Operation.payment({
      destination: receiverPublicKey,
      asset: usdc,
      amount: "10.00"
    }))
    .setTimeout(30)
    .build();
    ```
  </Step>

  <Step title="Sign and Sponsor">
    Alice signs the transaction to authorize the payment, then your app sends it to Grat for sponsorship.

    ```typescript theme={null}
    paymentTx.sign(senderKp);

    console.log("Sponsoring USDC payment...");
    const result = await grat.sponsor(paymentTx);

    console.log("Success! Hash:", result.hash);
    ```
  </Step>

  <Step title="Verify the Payment">
    Verify the transaction hash on [Stellar Expert](https://stellar.expert/explorer/testnet). The record will show that Alice's balance decreased by 10 USDC, while Grat's channel account paid the native XLM fee.
  </Step>
</Steps>

<Note>
  This guide uses the Testnet USDC issuer address. For Mainnet, you must use the official [Circle USDC issuer address](https://stellar.expert/explorer/public/asset/USDC-GA5ZSEJYB37JRC5AVCIA5MOP4RA57M773HIK7F64OXOBH3C326YF352H-1).
</Note>

[View on GitHub](https://github.com/gratnetwork/grat)