Check a tax ID format

Why one generic pattern doesn't work

Every country invents its own tax ID from scratch, so a validator that treats them all the same way is guaranteed to be wrong somewhere. Mexico's RFC mixes letters from a person's name with a birth date and a homoclave; Brazil's CPF and CNPJ each carry two check digits computed with their own weighted algorithm; Argentina's CUIT encodes a check digit using modulo 11 over an eleven-digit string. The tax id validation api keeps a distinct rule set per country and ID type instead of forcing every identifier through the same regular expression, which is the only way to catch a genuinely malformed number without also rejecting a valid one that just looks unusual.

Who ends up needing this

Invoicing platforms operating in Latin America must get the tax ID right before a fiscal document is even generated, since several tax authorities reject the document outright on a bad ID. Payroll and HR systems onboarding contractors across borders need the same check for withholding and reporting. KYC and onboarding flows at fintechs and marketplaces use it as a first, cheap filter before a heavier identity-verification step. Anyone collecting a tax ID from a form and storing it for later use is one typo away from a downstream rejection this endpoint is built to prevent.

The request cycle

Call POST /verify/tax-id with the identifier and the country, and the response comes back immediately with a task_id while the actual check runs asynchronously. The result reports whether the format is valid for that country's ID type, which check-digit algorithm was applied when one exists, and a plain reason when validation fails. A task that fails outright retries three times before returning a clear error, and a failed task is never billed.

A patchwork built over a century of tax administration

National tax identifiers weren't designed together; each was introduced independently, often decades apart, as tax authorities modernized their own record-keeping — some as early as the mid-20th century, others as recently as the digital-invoicing mandates of the last fifteen years. That independent history is exactly why formats diverge so widely in length, structure and check-digit logic. Maintaining accurate rules for more than 40 countries means tracking each authority's own specification rather than approximating from a handful of well-known formats.

Fitting into onboarding and invoicing pipelines

Because the response is structured JSON delivered by webhook, it plugs directly into signup forms, invoicing engines and periodic data-quality sweeps: validate a tax ID inline before a fiscal document is generated, gate contractor onboarding on a passing check, or run an existing customer table through the endpoint to flag records worth fixing before an audit. Access requires prepaid balance, which is what keeps the service fast and abuse-free, and each check is a flat published $0.002 with no bundled credits to reconcile.