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Several fees can apply when you spend from a Unified Balance, including a custom fee you can implement. This page explains which fees apply, how funds move through a spend and how that changes the Unified Balance total, and best practices for custom fees. Fees apply only on spends, not deposits.

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Fees breakdown

Each spend can include the following fees:
FeeWhen it appliesAmountRecipient
Custom spend feeConditionally. When you implement custom spend fees.You define (carved from the spend amount).90% to your fee recipient; 10% to Arc
Gateway protocol feeConditionally. On spends where the source and destination differ (crosschain).0.5 basis points (0.005%) of the spend amount from the Unified Balance at spend time; 0 if same blockchain.Circle Gateway (protocol underlying Unified Balance)
GasAlways. On spends that execute burn intents on source blockchains.Varies by source blockchain and network conditions; incurred per burn intent on source.Source blockchain
Forwarding Service feeConditionally. When you use the Forwarding Service for the destination mint.Per Forwarding Service fees. Deducted from amount minted on destination.Circle

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Total balance and funds flow

The following example shows what happens when a user spends 500 USDC from a Unified Balance of 1,000 USDC (previously deposited), you collect a 5 USDC custom fee on that spend, and the Forwarding Service is enabled:
1

User deposits into the Unified Balance

The user previously deposited 1,000 USDC from their wallet on the source blockchain into the Unified Balance.
2

User requests the spend on the destination blockchain

The user requests to spend 500 USDC on the destination blockchain.
3

You add a custom spend fee

You add a 5 USDC custom fee to the spend.
4

User signs burn intents on the source chains

The user’s source wallet signs three burn intents that move:
  • 495 USDC (the spend amount minus the 5 USDC custom fee) toward the destination mint.
  • 0.50 USDC (10% of the custom fee) to Arc.
  • 4.50 USDC (90% of the custom fee) to your fee recipient.
5

Circle Gateway applies the cross-chain transfer fee

Circle Gateway deducts a 0.025 USDC transfer fee from the Unified Balance (0.005% of 500 USDC). For a same-chain spend, this fee is 0.
6

Source chains deduct gas for the burn intents

The source blockchains deduct 0.03 USDC from the Unified Balance as gas for the three burn intents.
7

Forwarding Service deducts the destination mint fee

The Forwarding Service deducts its fee (0.20 USDC in this example) from the amount to be minted on the destination blockchain.
8

Recipient receives funds on the destination blockchain

The recipient’s destination wallet receives 494.80 USDC on the destination blockchain:
  • 495 USDC minted.
  • Deduct 0.20 USDC Forwarding Service fee.
  • Net received: 494.80 USDC.
9

Unified Balance shows the updated total

After the spend, the user’s Unified Balance total is 499.945 USDC:
  • Started at 1,000 USDC.
  • Deduct 500 USDC spend amount.
  • Deduct 0.025 USDC Gateway transfer fee.
  • Deduct 0.03 USDC gas.
  • Remaining: 499.945 USDC.
This flow and Unified Balance running total is illustrated in the following diagram.

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Best practices for custom fees

Follow these best practices when implementing custom fees:
  • Use a fee recipient address on the source blockchain. Do not use an address on the destination.
  • Before the user confirms a spend, show:
    • Unified Balance summary: starting balance, each deduction (spend amount, Gateway transfer fee when applicable, gas), and remaining balance.
    • Spend summary: requested spend amount, fee breakdown (custom fee and Forwarding Service fee when applicable), and net amount credited on the destination.
  • Return human-readable decimal strings. For example, return "10" rather than "10000000" for 10 USDC. App Kit handles base-unit conversion internally.
  • Validate that the user’s Unified Balance can cover the spend amount, the Gateway protocol fee, and gas. For gas and fee estimates, see estimate spend fees. Example check:
TypeScript
// Example: ensure the balance covers spend + custom fee + Gateway fee + gas estimate
const amount = "500"; // spend amount in USDC (human-readable decimal string)
const customFee = "5"; // your custom fee in USDC
const sameChain = false; // true when source and destination blockchain are the same
const gatewayFee = sameChain ? 0 : parseFloat(amount) * 0.00005; // 0.005% when crosschain
const gasEstimate = 0.05; // replace with a blockchain-appropriate estimate
const userBalance = parseFloat("1000"); // placeholder; in production parse totalConfirmedBalance from kit.unifiedBalance.getBalances
const requiredBalance =
  parseFloat(amount) + parseFloat(customFee) + gatewayFee + gasEstimate;
if (userBalance < requiredBalance) {
  throw new Error(`Insufficient balance. Need ${requiredBalance} USDC`);
}
// requiredBalance is about 505.075 USDC here (500 + 5 + 0.025 + 0.05)