Brazilian NFe Access Key Validator

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what does the NFe access key mean

What each digit of the NFe access key means

An NFe access key is not a random number, it is the concatenation of 9 fixed-length fields, each with a specific meaning defined by the Manual de Orientação do Contribuinte.

The 9 blocks, from the first to the last digit

From position 1 to 44: cUF (2 digits, the issuer's state IBGE code), AAMM (4 digits, issuance year and month), CNPJ (14 digits, the issuer's), mod (2 digits, 55 for NFe or 65 for NFCe), series (3 digits), invoice number (9 digits), emission type (1 digit, normal or a contingency mode), a random numeric code (8 digits), and finally the check digit (1 digit), computed in modulo 11 over the previous 43 digits.
Because every field has a fixed length and they are concatenated with no separator, any 44-digit key can be decoded just by slicing the string at the right offsets, with no external lookup needed, exactly what this tool does locally in the browser.

Example decoding

Decoded synthetic key

Input: 35240111222333000199550010000123451123456784
Expected output: SP · 01/2024 · CNPJ 11.222.333/0001-99 · NF-e · série 001 · nº 12345

cUF=35 (SP), AAMM=2401 (January 2024), mod=55 (NFe), all read directly from the fixed offsets.

Same key with a swapped check digit

Input: 35240111222333000199550010000123451123456789
Expected output: campos corretos, mas dígito não confere

All 43 leading digits are still decodable, only digit 44 (the check digit) fails verification.

Full tool FAQ

Does this tool query SEFAZ to check whether the invoice is real?

No, and it never will. It only decodes the fields and recomputes the check digit from the pasted key itself, entirely in your browser.

What do the 44 digits of the access key mean?

How is the check digit (44th digit) calculated?

What does the 'check digit mismatch' status mean?

Are model 55 and model 65 the same thing?

Does the generated sample key correspond to a real invoice?

Why doesn't the key have punctuation like a CPF or CNPJ?

Does a correct check digit guarantee the NFe was not canceled?

Frequently asked questions

Is the access key the same as the invoice number?

No. The invoice number (nNF) is just one of the 9 fields within the key, occupying positions 26 to 34. The full key combines that number with the state, date, CNPJ, model, series and other fields.

Why does the key have no letters, only digits?

Because every field is defined as numeric in the MOC layout, including the CNPJ (14 digits) and the state IBGE code. This simplifies both generation and reading by systems and barcodes/QR codes.

Can I tell the issuance date just by looking at the key?

Yes, partially: digits 3 through 6 (AAMM) give the year (2 digits) and the month, but not the exact day, which is not part of the access key.

Next steps

The 9 blocks, from the first to the last digit

From position 1 to 44: cUF (2 digits, the issuer's state IBGE code), AAMM (4 digits, issuance year and month), CNPJ (14 digits, the issuer's), mod (2 digits, 55 for NFe or 65 for NFCe), series (3 digits), invoice number (9 digits), emission type (1 digit, normal or a contingency mode), a random numeric code (8 digits), and finally the check digit (1 digit), computed in modulo 11 over the previous 43 digits.

Because every field has a fixed length and they are concatenated with no separator, any 44-digit key can be decoded just by slicing the string at the right offsets, with no external lookup needed, exactly what this tool does locally in the browser.

Example decoding

Decoded synthetic key

Input: 35240111222333000199550010000123451123456784
Expected output: SP · 01/2024 · CNPJ 11.222.333/0001-99 · NF-e · série 001 · nº 12345

cUF=35 (SP), AAMM=2401 (January 2024), mod=55 (NFe), all read directly from the fixed offsets.

Same key with a swapped check digit

Input: 35240111222333000199550010000123451123456789
Expected output: campos corretos, mas dígito não confere

All 43 leading digits are still decodable, only digit 44 (the check digit) fails verification.

Full tool FAQ

Does this tool query SEFAZ to check whether the invoice is real?

No, and it never will. It only decodes the fields and recomputes the check digit from the pasted key itself, entirely in your browser.

What do the 44 digits of the access key mean?

How is the check digit (44th digit) calculated?

What does the 'check digit mismatch' status mean?

Are model 55 and model 65 the same thing?

Does the generated sample key correspond to a real invoice?

Why doesn't the key have punctuation like a CPF or CNPJ?

Does a correct check digit guarantee the NFe was not canceled?

Frequently asked questions

Is the access key the same as the invoice number?

No. The invoice number (nNF) is just one of the 9 fields within the key, occupying positions 26 to 34. The full key combines that number with the state, date, CNPJ, model, series and other fields.

Why does the key have no letters, only digits?

Because every field is defined as numeric in the MOC layout, including the CNPJ (14 digits) and the state IBGE code. This simplifies both generation and reading by systems and barcodes/QR codes.

Can I tell the issuance date just by looking at the key?

Yes, partially: digits 3 through 6 (AAMM) give the year (2 digits) and the month, but not the exact day, which is not part of the access key.