TIN (Taxpayer Identification Number)

A Taxpayer Identification Number (TIN) is the umbrella term the IRS uses for any nine-digit identifier that is used on federal tax filings to identify a taxpayer. There are five flavors of TIN, only four of which are issued by the IRS, per the official IRS Taxpayer Identification Numbers page. Every withholding form, information return and federal tax return depends on the correct TIN appearing for both payer and payee.

How a TIN Works

A TIN is the primary key that ties a person or entity to the IRS’s records. The IRS uses TINs to:

• Match information returns (1099, 1042-S, W-2, etc.) to the taxpayer’s account
• Process refunds, payments and notices
• Enforce backup withholding when name and TIN do not match
• Track filing history and detect duplicates or substitutes

A taxpayer typically has exactly one TIN of each applicable type. An individual who later becomes SSN-eligible after holding an ITIN must rescind the ITIN and use the SSN going forward. An entity that converts legal form may need to apply for a new EIN.

The five TIN types and their issuers are as follows:

This split between issuers is one of the most common misconceptions. The SSN is issued by the Social Security Administration, not the IRS. The other four are all IRS-issued.

Who Needs It

Anyone who appears on a federal tax filing in any capacity needs a TIN.

• A US employee needs an SSN, and the employer uses it on Form W-2 and Form 941.
• A US business needs an EIN to file employment, excise or income tax returns and to issue 1099s.
• A US-based independent contractor provides their SSN or EIN to the payer on Form W-9 before the first payment.
• A foreign individual contractor without an SSN but with US-source income obtains an ITIN and uses it on Form W-8BEN or Form 8233.
• A foreign entity receiving US-source income obtains an EIN and uses it on Form W-8BEN-E.
• A paid tax preparer must have a PTIN under IRC section 6109 and the implementing regulations.

A US payer that pays a contractor without a valid TIN must apply 24% backup withholding under IRC section 3406.

Filing Deadlines

TINs themselves do not have a filing deadline, but the activities that depend on them do. Key timing rules:

• Get the TIN before payment. Payers should collect the TIN on Form W-9 or Form W-8 before the first reportable payment. Late collection exposes the payer to backup withholding obligations and information-return penalties.
• TIN matching before 1099 filing. Payers can run the IRS TIN Matching service on each W-9 before filing. Most filers match in batches before the January 31 1099-NEC deadline.
• EIN issuance. Online EIN applications produce a TIN immediately for US-principal-place-of-business filers. International filers using Form SS-4 by phone, fax or mail can wait days to weeks. See the IRS Apply for an EIN online page.
• ITIN issuance. ITINs take 7 weeks during off-peak periods, 9 to 11 weeks during peak season or for international applicants, per the Individual Taxpayer Identification Number page.
• ITIN expiration. ITINs expire after three consecutive years of non-use on a federal return.

Common Mistakes

• Treating ITIN as a substitute for SSN. An ITIN-holder is generally not work-authorized. Putting an ITIN on a W-9 in place of an SSN is wrong if the holder is not a US person.
• Skipping TIN matching. Filing 1099s without first running IRS TIN matching is a leading cause of CP-2100 backup withholding notices the following year.
• Mixing up issuers. SSNs come from SSA, and everything else comes from the IRS. Calling the IRS to ask about an SSN status sends taxpayers down the wrong path.
• Reusing an EIN after entity change. Some legal-structure changes require a new EIN. Reusing the old one can invalidate filings.
• Letting an ITIN expire. Three years of non-use kills the ITIN. Contractors planning to claim a treaty rate need a live, current ITIN at the time of the claim.

Related Forms

• EIN (Employer Identification Number): the entity-level TIN.
• ITIN (Individual Taxpayer Identification Number): the individual-level TIN for non-SSN-eligible filers.
• Form W-9: the US-person form that collects SSN or EIN.
• Form W-8BEN and Form W-8BEN-E: the foreign-person forms that collect ITIN, EIN or a foreign TIN.
• Form 1099-NEC and Form 1042-S: the year-end information returns that fail validation when the TIN is wrong.

Omnivoo Contract Management collects the right TIN for every contractor (SSN, EIN or ITIN), runs IRS TIN matching at onboarding, and stores the verified TIN against every downstream 1099 or 1042-S filing.