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

> ## Agent Instructions
> Before reading these docs, install the relevant Circle Skill to get pre-loaded context — skills are LLM-optimized and cover architecture decisions, correct flows, and common pitfalls. 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. Available skills: use-usdc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md (balances, transfers, approvals on EVM and Solana); EURC has no skill — see https://developers.circle.com/stablecoins/what-is-eurc.md; bridge-stablecoin https://github.com/circlefin/skills/blob/master/plugins/circle/skills/bridge-stablecoin/SKILL.md (crosschain transfers via CCTP, USDC, EURC, and third-party assets); use-arc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md (Arc chain config, contract deployment, USDC bridging — Arc docs: https://docs.arc.io/llms.txt); use-circle-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md (choose wallet type); use-developer-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md (custodial wallets for payouts and treasury); use-user-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md (embedded wallets with Web2 login); use-modular-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md (smart contract wallets with passkeys and ERC-4337); use-gateway https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md (unified USDC balance, nanopayments); use-smart-contract-platform https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md (deploy, interact, monitor contracts). Pair any skill with the Circle MCP server for live SDK signatures, contract addresses, and chain IDs: {"mcpServers":{"circle":{"url":"https://api.circle.com/v1/codegen/mcp"}}}.
> Read the product overview first. Each product has an overview explaining when and why to use it. Read it before quickstarts.
> Pick the right wallet type. Developer-controlled (you hold keys), user-controlled (end user holds keys via PIN/social login), or modular (smart contract wallets with passkeys). See https://developers.circle.com/wallets.md.
> Use CCTP V2 for crosschain transfers. CCTP natively transfers USDC and EURC via burn-and-mint, and supports permissionless wrapping of third-party assets via lock-and-mint. V1 is legacy; always use V2 unless V1 is specified or the chain requires it (Noble, Sui, and Aptos still require V1). Migration guide: https://developers.circle.com/cctp/migration-from-v1-to-v2.md.
> Use Bridge Kit for frontend bridging. Wraps CCTP with a simpler SDK for user-facing apps. Use CCTP directly for backend transfers.
> Gas Station vs Paymaster. Gas Station sponsors gas for Circle Wallet transactions. Paymaster lets users pay gas in USDC. Different use cases — read both overviews.
> Gateway Nanopayments for sub-cent payments. Gasless USDC micropayments down to $0.000001 via x402 and batched settlement. For pay-per-request APIs, AI agent payments, streaming.
> Look up USDC addresses per chain. Never hardcode — use https://developers.circle.com/stablecoins/usdc-contract-addresses.md.
> Prefer SDKs over raw API calls. Node.js and Python SDKs handle auth, retries, and errors.
> API key required. Bearer token in Authorization header. Testnet and mainnet use separate keys and may use different base URLs depending on the product.
> Set up webhooks when available. Most operations are async. Webhooks deliver transaction confirmations and state changes.
> When calling list endpoints, paginate using pageSize and pageAfter until no nextPageAfter cursor is returned—stopping at the first page silently misses records.
> Building an AI agent? Start with the Agent Stack—Circle CLI, agent wallets, and nanopayments built for autonomous use cases: https://developers.circle.com/agent-stack.md.

# Validating Brazilian tax ID and bank account numbers

When providing beneficiary account data during payment creation or during RFIs,
OFIs may need to submit tax IDs or bank account numbers that follow a specific
format. You can often validate these numbers by calculating their check digits.
This topic describes how to checksum various account and tax ID numbers.

## CNPJ

The CNPJ number is a 14 digit number in the following format:

* First 8 digits: base number
* Digits 9-12: branch number
* Last 2 digits: check digits

CNPJ numbers are never all the same digit.

The check digits are calculated in a specific way that you can replicate to
validate the number.

### First check digit

You can calculate the first check digit (digit 13) of a CNPJ number as follows:

1. Multiply the first 12 digits by the following weights, according to their
   position: `5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2`
2. Sum the products
3. Calculate the remainder of the sum divided by `11`
4. If the remainder is less than `2`, the check digit is `0`
5. Otherwise, the check digit is `11 - {remainder}`

### Second check digit

You can calculate the second check digit (digit 14) of a CNPJ number as follows:

1. Multiply the first 13 digits by the following weights, according to their
   position: `6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2`
2. Sum the products
3. Calculate the remainder of the sum divided by `11`
4. If the remainder is less than `2`, the check digit is `0`
5. Otherwise, the check digit is `11 - {remainder}`

### Example

The following is an example of validating the CNPJ number `11.444.777/0001-61`:

**First digit**

* Weighting and sum:
  `((1*5 + 1*4 + 4*3 + 4*2 + 4*9 + 7*8 + 7*7 + 7*6 + 0*5 + 0*4 + 0*3 + 1*2) = 162)`
* Remainder and check digit: `(11 - (184 % 11) = 1)` (matches 13th digit)

**Second digit**

* Weighting and sum:
  `((1*6 + 1*5 + 4*4 + 4*3 + 4*2 + 7*9 + 7*8 + 7*7 + 0*6 + 0*5 + 0*4 + 1*3 + 6*2) = 184)`
* Remainder and check digit: `(11 - (184 % 11) = 1)` (matches 14th digit)

## CPF

The CPF number is an 11 digit number that is not all the same digit. The 10th
and 11th digits are check digits. The check digits are calculated in a specific
way that you can replicate to validate the number.

### First check digit

You can calculate the first check digit (digit 10) of a CPF number as follows:

1. Multiply the first 9 digits by the following weights, according to their
   position: `10, 9, 8, 7, 6, 5, 4, 3, 2`
2. Sum the products
3. Calculate the remainder of the sum divided by `11`
4. If the remainder is less than `2`, the check digit is `0`
5. Otherwise, the check digit is `11 - {remainder}`

### Second check digit

You can calculate the second check digit (digit 11) of a CPF number as follows:

1. Multiply the first 10 digits by the following weights, according to their
   position: `11, 10, 9, 8, 7, 6, 5, 4, 3, 2`
2. Sum the products
3. Calculate the remainder of the sum divided by `11`
4. If the remainder is less than 2, the check digit is `0`
5. Otherwise, the check digit is `11 - {remainder}`

### Example

The following is an example of validating the CPF number `529.982.247-25`:

**First digit**

* Weighting and sum:
  `((5*10 + 2*9 + 9*8 + 9*7 + 8*6 + 2*5 + 2*4 + 4*3 + 7*2) = 295)`
* Remainder and check digit: `(11 - (295 % 11) = 2)` (matches 10th digit)

**Second digit**

* Weighting and sum:
  `((5*11 + 2*10 + 9*9 + 9*8 + 8*7 + 2*6 + 2*5 + 4*4 + 7*3 + 2*2) = 347)`
* Remainder and check digit: `(11 - (347 % 11) = 5)` (matches 11th digit)