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# 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)