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

> ## Agent Instructions
> Before reading these docs, install the Circle Skill for Arc to get pre-loaded context: use-arc (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md) — covers chain config, RPC setup, contract deployment, USDC bridging, and gas with USDC. In Claude Code: run /plugin marketplace add circlefin/skills then /plugin install circle-skills@circle. With Vercel Skills CLI: run npx skills add circlefin/skills.
> USDC is the gas token. Arc uses USDC for gas fees, not ETH. Configure gas payment in USDC when submitting transactions.
> Read EVM differences before writing Arc code. Arc targets the Osaka EVM baseline. Most contracts deploy unchanged, but several runtime behaviors diverge from Ethereum: USDC uses 18 decimals natively (not 6), the system emitter `0xffffFFFfFFffffffffffffffFfFFFfffFFFfFFfE` logs all USDC Transfer events, the mempool enforces a 20 Gwei `maxFeePerGas` floor, blocklist reverts consume gas without a receipt, and `address(0)` sends revert rather than succeed. https://docs.arc.io/arc/references/evm-differences.md is the canonical reference for all Arc-specific runtime behaviors. Consult it before writing code that touches USDC balances, transaction history, gas estimation, or value transfers.
> Sub-second finality. Transactions are final in under 1 second. No need to wait for multiple block confirmations.
> Use App Kits for multichain payment and liquidity capabilities. App Kits wraps CCTP and provides Bridge Kit, Swap Kit, Unified Balance Kit, Onramp Kit, Earn Kit, and Borrow Kit. Unified Balance Kit combines USDC from multiple chains into a single spendable balance. Earn Kit integrates earn opportunities into your app. Borrow Kit lets users borrow USDC against cirBTC collateral on Arc.
> Use Arc Foundry for contract development. Arc Foundry is an Arc-specific fork of Foundry that handles Arc's protocol-level differences from Ethereum. It provides arc-forge, arc-cast, and arc-anvil. Install it before deploying contracts: https://docs.arc.io/arc/tutorials/install-arc-foundry.md.
> Arc is available on both Testnet and Mainnet. See https://docs.arc.io/arc/references/connect-to-arc.md for RPC endpoints and https://faucet.circle.com for testnet tokens.
> Always check Contract Addresses: https://docs.arc.io/arc/references/contract-addresses.md
> Building beyond Arc? Circle offers skills for the full platform: use-usdc (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md), use-circle-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md), use-developer-controlled-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md), use-user-controlled-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md), use-modular-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md), use-gateway (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md), use-smart-contract-platform (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md). Full Circle developer docs: https://developers.circle.com/llms.txt.

# How-to: Pay down a loan

> Repay USDC debt, close a loan in full, and withdraw cirBTC collateral from a Borrow loan

Pay down a Borrow loan with a partial repayment, a full close, or a collateral
withdrawal. Each operation addresses the loan by `loanId`.

## Prerequisites

Before you begin, ensure that you've:

* [Installed the App Kit SDK](/app-kit/tutorials/installation) and an adapter
* Opened a loan with debt or collateral to withdraw

## Repay part of a loan

Call `repay` with the loan's `loanId` and the USDC amount. The SDK rejects the
request before signing if `repayAmount` exceeds outstanding debt. Use
`closeLoan` for a full payoff.

```typescript TypeScript theme={null}
const result = await kit.borrow.repay({
  from: { adapter, chain: "Arc_Testnet" },
  loanId: "11111111-1111-4111-8111-111111111111",
  repayAmount: "100.0",
});
```

## Close a loan in full

Call `closeLoan` to repay all outstanding debt and withdraw all collateral in a
single atomic batch. The SDK uses share-based payoff math and may pull more USDC
than needed, up to your `slippageBps` bound, refunding any surplus.

```typescript TypeScript theme={null}
const result = await kit.borrow.closeLoan({
  from: { adapter, chain: "Arc_Testnet" },
  loanId: "11111111-1111-4111-8111-111111111111",
});

if (result.status === "confirmed") {
  console.log("Repaid:", result.amountRepaid.amount);
  console.log("Collateral withdrawn:", result.collateralWithdrawn.amount);
}
```

To preview a full close before signing, see
[Preview Borrow operations](/app-kit/howtos/borrow/preview-a-loan-operation#preview-a-full-close).

## Withdraw collateral

Call `withdrawCollateralRepayIfNeeded` to release cirBTC from a loan. The SDK
sizes any repayment needed to keep the loan healthy after the withdrawal and
pays it from the wallet's USDC balance in the same atomic batch. If the
repayment covers the entire debt, the withdrawal closes the loan.

```typescript TypeScript theme={null}
const result = await kit.borrow.withdrawCollateralRepayIfNeeded({
  from: { adapter, chain: "Arc_Testnet" },
  loanId: "11111111-1111-4111-8111-111111111111",
  collateralAmount: "0.01",
});
```

To preview a collateral withdrawal before signing, see
[Preview Borrow operations](/app-kit/howtos/borrow/preview-a-loan-operation#preview-withdrawing-collateral).