Use cases

Signup and checkout forms

Add TIN validation to signup and checkout forms

Signup and checkout forms are high-friction places to ask for tax data. TIN validation lets you catch obvious errors while the user is still present and able to fix the field.

Best for

Product and engineering teams building account creation, checkout, invoice, or tax-information forms.

The problem

A generic 'invalid tax ID' message makes users guess what went wrong. A structured validation response can tell the application whether the issue is length, characters, format, type, or checksum.

How TIN validation fits

  1. 1 Run validation after the user selects a country and leaves the TIN field, or on form submission.
  2. 2 Map failed validation checks to concise field-level messages.
  3. 3 Let users keep local punctuation while storing a clean normalised value.
  4. 4 Keep the API key on the server and return only the UI feedback your form needs.

Useful checks

Per-country validation before form submission completes

Field-level feedback for common input mistakes

Server-side API integration for API-key protection

Consistent handling across web app and API workflows

What it does not prove

TIN validation improves data quality at input time. It does not replace legal, tax, KYC, KYB, VAT, or government-record verification where those checks are required.