Eu vat id validate

eu-vat-id-validate · version 1.0.0 · Identifiers & check digits · free, no key needed

Detect the country from an EU/XI VAT id prefix and validate its format and, where defined, national checksum.

Use when you need to: validate an eu vat number · check a german ust-idnr checksum · is this a real italian partita iva.

Decide before calling

Read the versioned contract and the supported scope below. Reuse eu-vat-id-validate@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use eu-vat-id-validate@1.0.0 for validate an eu vat number. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

validate an eu vat number
check a german ust-idnr checksum
is this a real italian partita iva
detect the country from a vat id prefix
validate a northern ireland xi vat number
check a dutch btw sole proprietor id format
בדיקת מספר עוסק אירופאי

Not supported

a live VIES lookup to confirm the number is currently registered
a checksum for the 10 member states this family will not clean-room guess at (BG, CY, CZ, EE, IE, LT, LV, MT, RO, SK are format-only)
a VAT-id prefix outside the 28 recognised EU/XI codes (no generic/unknown-country mode)

Behavior

vat_id's first 2 characters (no case folding) must be one of the 28 recognised prefixes (AT, BE, BG, CY, CZ, DE, DK, EE, EL, ES, FI, FR, HR, HU, IE, IT, LT, LU, LV, MT, NL, PL, PT, RO, SE, SI, SK, XI), else {valid:false, reason:'unknown_prefix'} with country/prefix/number all null.
When country is supplied and disagrees with the detected prefix, {valid:false, reason:"country_mismatch"} is returned without evaluating the country’s own rules; the output’s country/prefix always report what was detected from vat_id, never the caller’s country argument.
Once the prefix is recognised (and country, if given, agrees), problems with number are reported in order: wrong_length, invalid_character, invalid_component, checksum_mismatch -- never thrown.
checksum is ’verified’ for AT, BE, DE, DK, EL, FI, FR, HR, HU, IT, LU, NL, PL, PT, SE, SI, XI, and for ES’s natural-person NIF/NIE branch; it is ’not_defined’ (format-only) for BG, CY, CZ, EE, IE, LT, LV, MT, RO, SK and ES’s CIF (legal-entity) branch, per the documented historical/algorithmic reasons in this tool’s spec. IE now matches a shape regex covering its pre-2013, 2013+ and old-style letter/symbol formats, but its check character is still not verified.
NL: 9-digit block then the literal letter ‘B’ then 2 digits; checksum ‘verified’: valid if EITHER the 9-digit block passes the elfproef (weights [9,8,7,6,5,4,3,2,-1], sum mod 11 == 0, the RSIN/BSN-derived legal-entity form) OR ISO/IEC 7064 MOD 97-10 over ‘NL’+number leaves remainder 1 (the sole-proprietor form issued since 2020-01-01); neither passing is checksum_mismatch. SI: 8 digits, leading digit not ‘0’ (invalid_component); weights [8,7,6,5,4,3,2] over the first 7 digits, a remainder of 0 has no valid check digit (checksum_mismatch outright), remainder 1 maps to check digit 0, otherwise expected = 11 - remainder.
DE and HR reuse the ISO/IEC 7064 MOD 11-10 recurrence (as in checkdigit-compute’s iso7064-mod11-10 preset); IT and the first 10 digits of SE reuse the standard Luhn algorithm; AT uses its own Luhn-derived formula (checksum over 7 digits, then (6 - sum) mod 10).
normalized is always vat_id unchanged; number is vat_id with the 2-character prefix removed, unchanged (no separator stripping -- callers submit the compact form). data_version is always "eu-vat-prefixes-2026-09-28".
Pure integer and table-lookup arithmetic; no locale, clock, or randomness; this tool never calls VIES or any other network service; identical output across runs for the same input.

Input

vat_id (string, required): min length 3; max length 14
country (string, optional): pattern ^[A-Z]{2}$

Output

valid (boolean, required)
reason (one of null, "unknown_prefix", "country_mismatch", "wrong_length", "invalid_character", "invalid_component", "checksum_mismatch", required)
country (string or null, required): pattern ^[A-Z]{2}$
prefix (string or null, required): pattern ^[A-Z]{2}$
number (string or null, required): min length 1; max length 12
normalized (string, required): min length 3; max length 14
checksum (one of "verified", "not_defined", required)
data_version (constant "eu-vat-prefixes-2026-09-28", required)

Limits

max vat id bytes: 14

Example

Request input:

{
  "vat_id": "DE811569869"
}

Response:

{
  "result": {
    "valid": true,
    "reason": null,
    "country": "DE",
    "prefix": "DE",
    "number": "811569869",
    "normalized": "DE811569869",
    "checksum": "verified",
    "data_version": "eu-vat-prefixes-2026-09-28"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "eu-vat-id-validate",
  "version": "1.0.0",
  "input": {
    "vat_id": "DE811569869"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/eu-vat-id-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"vat_id":"DE811569869"}'

The machine-readable contract is at /v1/tools/eu-vat-id-validate/versions/1.0.0.

CLI

node cli.mjs run eu-vat-id-validate 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

National id validate: Validate a personal identity number’s format and, where defined, checksum for one of 14 national schemes.
Imo number validate: Validate a 7-digit IMO ship identification number's weighted mod-10 check digit, with or without the 'IMO ' prefix.
Se personnummer parse: Parse a Swedish personnummer/samordningsnummer: resolve its century, return birth date, sex and Luhn validity.
Tax id validate: Validate a taxpayer/business registration number’s format and, where defined, checksum for one of 12 national schemes.
Isin validate: Validate a 12-character ISIN's ISO 6166 Luhn check digit and parse its country prefix, NSIN and NSIN scheme.
Ismn validate: Validate an ISMN's EAN mod 10 check digit in M-form or 979-0 form and return the canonical 13-digit form.