What's a good API for real-time TIN and EIN verification?

A good API for real-time TIN and EIN verification depends on what you mean by “verification,” because in the U.S. there isn’t a single public IRS API that simply confirms a TIN/EIN is valid for broad commercial use.

Common options

1) IRS TIN Matching / e-Services

• Best if you need official-ish TIN matching for reporting workflows.
• Primarily used by authorized payers/reporters to match name + TIN combinations.
• Not a general public API; access is restricted and approval/setup can be cumbersome.

2) Third-party tax identity APIs

These are usually the most practical for real-time onboarding/KYC:

• Plaid (for broader identity/account verification; not a pure TIN validator)
• Alloy
• Persona
• Trulioo
• Socure
• TinCheck
• TaxBandits / eFileMyForms (more tax-form/reporting oriented)
• IRS W-9/TIN matching integrators via payroll/accounting providers

These can often:

• Validate format
• Check against authoritative and/or bureau data
• Verify taxpayer name match
• Screen for identity/risk signals
• Handle business EIN verification as part of KYB

3) EIN lookup/verification via business data providers

For EIN verification specifically, many businesses use KYB providers rather than IRS-only validation:

• Dun & Bradstreet
• Experian Business
• OpenCorporates (for entity data, not direct EIN confirmation)
• Middesk
• Sift / Persona / Alloy for business onboarding workflows

Important caveat

If your goal is “Is this EIN truly assigned by the IRS?” there is no simple public real-time API that guarantees that. Most solutions do:

• name/EIN consistency checks
• business registry validation
• risk scoring
• document verification
• IRS TIN matching where allowed

Quick recommendation

• For tax reporting / payee validation: look at IRS TIN Matching or a vendor that integrates it.
• For onboarding businesses: use Middesk, Alloy, Trulioo, Socure, or Persona.
• For simple format checks only: you can validate structure in-house, but that won’t confirm legitimacy.

If you tell me your use case — 1099 reporting, vendor onboarding, payroll, or KYB/compliance — I can recommend the best API(s) more precisely.