About

A CNPJ (Cadastro Nacional da Pessoa Jurídica) is a 14-digit identifier assigned by Brazil's Receita Federal to every registered legal entity. The first 8 digits form the company base registration, digits 9 through 12 encode the branch number (where 0001 denotes headquarters), and the final 2 digits are check digits computed via a weighted mod-11 algorithm. Using fabricated or structurally invalid CNPJs in development environments causes silent failures in fiscal APIs, payment gateways, and nota fiscal emission systems. This tool generates CNPJs that pass algorithmic validation but correspond to no real entity. They are intended exclusively for software testing, form validation, and database seeding.

The generator produces numbers that satisfy the exact verification procedure defined by Instrução Normativa RFB. Note: generated CNPJs are mathematically valid but fictitious. Using them in official documents or tax filings constitutes fraud under Brazilian law (Lei 8.137/90). For bulk test suites, the tool supports batch generation of up to 100 numbers per run with optional formatting masks.

Formulas

The CNPJ check digits are computed sequentially. First, the 12-digit base (registration + branch) is multiplied element-wise by a weight vector, summed, and reduced modulo 11.

S₁ = 12∑i=1 d_i × w_1,i

r₁ = S₁ mod 11

C₁ =

{

0 if r₁ < 211 − r₁ otherwise

The second check digit uses the same procedure over 13 digits (base + first check digit) with weight vector w₂.

S₂ = 13∑i=1 d_i × w_2,i

C₂ =

{

0 if (S₂ mod 11) < 211 − (S₂ mod 11) otherwise

Where d_i is the i-th digit, w₁ = [5,4,3,2,9,8,7,6,5,4,3,2], and w₂ = [6,5,4,3,2,9,8,7,6,5,4,3,2]. The final CNPJ is the concatenation of base digits, branch digits, C₁, and C₂.

Reference Data

Position	Digits	Description	Example
1-8	8	Company base registration number	11222333
9-12	4	Branch/establishment number (0001 = HQ)	0001
13	1	First check digit (mod-11 with weights 5 - 2,9 - 2)	8
14	1	Second check digit (mod-11 with weights 6 - 2,9 - 2)	1
Weight Sequences for Check Digit Calculation
1st digit	12 weights	5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2	Applied to positions 1-12
2nd digit	13 weights	6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2	Applied to positions 1-13
Mod-11 Remainder Rules
Remainder	< 2	Check digit = 0	remainder 0 or 1 → digit 0
Remainder	≥ 2	Check digit = 11 − remainder	remainder 4 → digit 7
Common Formatting Patterns
Formatted	18 chars	XX.XXX.XXX/XXXX-XX	11.222.333/0001-81
Unformatted	14 chars	XXXXXXXXXXXXXX	11222333000181
Known Invalid Sequences (Reject List)
00000000000000	All zeros	Passes mod-11 but rejected by Receita Federal	Must be excluded
11111111111111	All ones	Passes mod-11 but rejected by Receita Federal	Must be excluded
22222222222222	All twos	Same-digit sequences are invalid	Must be excluded
33333333333333 … 99999999999999	All same	All repeated-digit CNPJs are excluded	Must be excluded

Frequently Asked Questions

No. The generator creates numbers that are algorithmically valid (they pass the mod-11 check digit verification) but correspond to no real legal entity. They are fictitious identifiers suitable for software testing, form validation, and database seeding. Using them on official documents or tax filings is a criminal offense under Lei 8.137/90.

All 10 repeated-digit CNPJs (00000000000000 through 99999999999999) technically pass the mod-11 check digit algorithm. However, the Receita Federal explicitly rejects these sequences during validation. Any serious CNPJ validator must blacklist them. The generator follows this rule to produce numbers that pass real-world validation routines, not just the mathematical check.

Digits 9 through 12 encode the establishment number. The value 0001 indicates the company headquarters (matriz). Branch offices (filiais) receive sequential numbers starting from 0002. The generator defaults to 0001 but supports random branch numbers for testing multi-establishment scenarios.

The Luhn algorithm uses a fixed doubling pattern and mod-10 reduction. The CNPJ mod-11 algorithm uses variable weight vectors (5,4,3,2,9,8,7,6... cycling) and mod-11 reduction with a special rule: if the remainder is less than 2, the check digit is 0 rather than 11 minus the remainder. This prevents negative check digits and constrains results to the 0-9 range.

Yes. The tool includes a validation mode. Enter any 14-digit CNPJ (with or without formatting) and the validator recomputes both check digits independently. It reports whether each digit matches, identifies the exact point of failure if invalid, and flags blacklisted repeated-digit sequences.

No. The dots, slash, and hyphen are purely visual separators. The underlying 14-digit number is identical whether formatted or not. The formatting follows the standard pattern defined by the Receita Federal for printed documents and NFe (Nota Fiscal Eletrônica) fields.