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

# Build a Validity Transaction

> Sign and submit a validity transaction with Viem.

This guide uses an EIP-1559 transaction with Viem because it is the recommended transaction type. The API also supports signed legacy and EIP-2930 transactions.

<Warning>
  Validity Transactions are experimental. `base_sendRawTransactionValidity` is currently available on Vibenet.
</Warning>

## 1. Create Predicates

Use `balance` or `storage` to wait for account or contract state. Use `block_number` and `flashblock_index` to constrain the candidate position. Every predicate must match.

```ts Predicate setup lines wrap expandable theme={null}
import type { Address, Hex } from 'viem';

const validity = [
  {
    type: 'balance',
    params: {
      address: '0x8ba1f109551bD432803012645Ac136ddd64DBA72' as Address,
      op: '>=',
      value: '0x1' as Hex,
    },
  },
  {
    type: 'storage',
    params: {
      address: '0x8ba1f109551bD432803012645Ac136ddd64DBA72' as Address,
      slot: '0x8' as Hex,
      op: '=',
      value: '0x2a' as Hex,
    },
  },
  {
    type: 'block_number',
    params: { op: '<=', value: '0x11a6a1' as Hex },
  },
  {
    type: 'flashblock_index',
    params: { op: '<=', value: '0x2' as Hex },
  },
] as const;
```

Omit `mask` to compare the full storage word. Use `flashblock_index` to target a position within a Flashblock.

## 2. Sign an EIP-1559 Transaction

Use the sender's next nonce. The signed payload becomes the first RPC parameter.

```ts Sign transaction lines wrap expandable theme={null}
import { createPublicClient, http, type Chain } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';

const client = createPublicClient({ chain, transport: http(rpcUrl) });
const account = privateKeyToAccount(privateKey);
const fees = await client.estimateFeesPerGas();
const nonce = await client.getTransactionCount({
  address: account.address,
  blockTag: 'latest',
});

const rawTransaction = await account.signTransaction({
  chainId: (chain as Chain).id,
  type: 'eip1559',
  nonce,
  to: '0x...' as Address,
  data: '0x...' as Hex,
  value: 0n,
  gas: 100_000n,
  maxFeePerGas: fees.maxFeePerGas,
  maxPriorityFeePerGas: fees.maxPriorityFeePerGas,
});
```

## 3. Submit the Transaction

Pass the signed transaction and `validity` as separate parameters.

```ts Submit transaction lines wrap expandable theme={null}
const response = await fetch(rpcUrl, {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    jsonrpc: '2.0',
    id: 1,
    method: 'base_sendRawTransactionValidity',
    params: [rawTransaction, { validity }],
  }),
});

const body = await response.json();
if (body.error) throw new Error(body.error.message);
const hash = body.result;
```

## 4. Check Inclusion

The RPC returns a transaction hash. Use [`eth_getTransactionReceipt`](/base-chain/api-reference/ethereum-json-rpc-api/eth_getTransactionReceipt) to check for an onchain receipt.

For field definitions, see [Validity Transaction RPC](/specifications/build-transaction/base_sendRawTransactionValidity).