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

# createBuyTransaction()

> Buy a token with a specified USD amount sourced from Primary Assets across chains.

The Universal Accounts SDK supports **buy/swap transactions** directly through the `createBuyTransaction()` method. This allows you to programmatically route an amount in **USD** into a target token (e.g., USDT on Arbitrum), without requiring the user to hold funds on the destination chain.

Once the transaction is created, it returns a `rootHash` value representing the payload to be signed. You then use your **signer** (in this case, Particle Auth) to sign the message, and pass the result into sendTransaction() to broadcast it:

<Note>
  You can specify the specific tokens you want to use as source for the swap by setting the `usePrimaryTokens` property in the `tradeConfig` object when initializing the Universal Account.

  ```ts theme={null}
  tradeConfig: {
      usePrimaryTokens: [SUPPORTED_TOKEN_TYPE.SOL],
    },
  ```
</Note>

```ts theme={null}
import { CHAIN_ID, UniversalAccount } from "@particle-network/universal-account-sdk";
import { useEthereum } from "@particle-network/authkit";

// extract the provider from Particle Auth
const { provider } = useEthereum();

// In your app
const transaction = await ua.createBuyTransaction({
  token: {
    chainId: CHAIN_ID.ARBITRUM_MAINNET_ONE,
    address: "0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9", // USDT on Arbitrum
  },
  amountInUSD: "10", // Target amount in USD sourced from primary assets held
});

const signature = await provider.signMessage(transaction.rootHash);
const result = await ua.sendTransaction(transaction, signature);

console.log("Explorer URL:", `https://universalx.app/activity/details?id=${result.transactionId}`);
```

The `sendTransaction` method will then return a `TransactionResult` object, which includes the transaction ID and other metadata.

<Card title="Sample Swap Transaction" icon="coin-front" href="https://github.com/soos3d/auth-universal-accounts/blob/main/auth-universal-demo/app/components/SendTransactionCard.tsx">
  See how to initiate a swap transaction in a demo Next.js app using both Particle Auth and Universal Accounts.
</Card>

## Next steps

<CardGroup cols="2">
  <Card title="Sell Transaction" icon="money-bill-trend-up" href="/universal-accounts/ua-reference/web/transactions/sell">
    `createSellTransaction()` — sell a token into a primary asset.
  </Card>

  <Card title="Conversion Transaction" icon="right-left" href="/universal-accounts/ua-reference/web/transactions/conversion">
    `createConvertTransaction()` — convert between primary assets.
  </Card>
</CardGroup>