Batch Payroll (1-to-N)

This guide shows how to send private payments to multiple recipients (1-to-N) using a batch transfer pattern. Ideal for payroll, contractor payments, and vendor disbursements.

Overview

The batch payroll pattern extends the single payment flow to handle multiple payees efficiently:

1. One wrap transaction for the total amount
2. One batch transfer to all deposit addresses
3. Individual redemptions per payee (can be batched with EIP-5792)

This reduces gas costs and simplifies the sender’s workflow while maintaining privacy for each recipient.

Key Differences from Single Payments

Aspect	Single Payment	Batch Payroll
Payment keys	1	N (one per payee)
Wrap transactions	1	1
Transfer transactions	1	1 (via batch proxy)
Redemption transactions	1	N (or batched)

Implementation

Setup

First, set up the environment and configuration:

import { Abi, Domain, IbcCoreRegistry } from "@unionlabs/payments";
import {
  Attestor,
  EvmPublicClient,
  EvmWalletClient,
  Payment,
  Prover,
} from "@unionlabs/payments/promises";
import * as Viem from "viem";
import * as ViemAccounts from "viem/accounts";
import * as ViemChains from "viem/chains";

const BASE_RPC = "https://base-mainnet.g.alchemy.com/v2/<redacted>";

const ATTESTOR_KEY =
  process.env.ATTESTOR_KEY ??
  "6af6f8068d38ebf6666b8db98f9b8b42959ab62646764bc290e663f7abb49eea";

const USDC_ADDRESS = Domain.Erc20Address(
  "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
);

const BASE_UNIVERSAL_CHAIN_ID = Domain.UniversalChainId.make("base.8453");
const CLIENT_ID = 5;

/**
 * Batch proxy contract for multi-recipient transfers.
 * This example uses Request Finance's ERC20BatchPayments contract.
 * You can deploy your own or use any contract with a compatible interface.
 * @see https://github.com/RequestNetwork/requestNetwork
 */
const BATCH_PROXY_ADDRESS: `0x${string}` =
  "0x0DD57FFe83a53bCbd657e234B16A3e74fEDb8fBA";
const BATCH_PROXY_ABI = [
  {
    inputs: [
      { name: "_tokenAddress", type: "address" },
      { name: "_recipients", type: "address[]" },
      { name: "_amounts", type: "uint256[]" },
      { name: "_paymentReferences", type: "bytes[]" },
      { name: "_feeAmounts", type: "uint256[]" },
      { name: "_feeAddress", type: "address" },
    ],
    name: "batchERC20PaymentsWithReference",
    outputs: [],
    stateMutability: "nonpayable",
    type: "function",
  },
] as const;

const privateKey = process.env.PRIVATE_KEY as `0x${string}`;
if (!privateKey) throw new Error("Please provide a PRIVATE_KEY as an env var.");

const walletAddress = ViemAccounts.privateKeyToAccount(privateKey).address;

Create SDK clients from viem:

const viemPublicClient = Viem.createPublicClient({
  chain: ViemChains.base,
  transport: Viem.http(BASE_RPC),
}) as Viem.PublicClient;

const viemWalletClient = Viem.createWalletClient({
  account: ViemAccounts.privateKeyToAccount(privateKey),
  chain: ViemChains.base,
  transport: Viem.http(BASE_RPC),
}) as Viem.WalletClient;

const publicClient = await EvmPublicClient.fromViem(viemPublicClient);
const walletClient = await EvmWalletClient.fromViem(viemWalletClient);

Initialize the Attestor and Prover services:

const attestor = await Attestor.make({ apiKey: ATTESTOR_KEY });
const prover = await Prover.make({});

Define payees

Create batch payment

Prepare wrap

Execute batch transfer

Update light client

Generate proofs

Get attestations

Submit redemptions

Privacy Guarantees

With batch payroll:

• Recipients cannot see other recipients’ payment amounts
• Recipients cannot see the sender’s total balance or other funds
• Sender maintains full visibility of all payments for accounting
• Attestor records each (depositAddress, beneficiary) pair for compliance

Next Steps

Single Payment Learn the fundamentals with a single payment flow.

Payroll Overview Understand the actors and requirements for private payroll.