ITIN (Individual Taxpayer Identification Number)

An ITIN (Individual Taxpayer Identification Number) is a nine-digit tax processing number that the IRS issues to people who have a US federal tax obligation but cannot get a Social Security Number. The IRS defines it as “a 9-digit number the IRS issues if you need a U.S. taxpayer identification number for federal tax purposes, but you aren’t eligible for a Social Security number (SSN),” on its Individual Taxpayer Identification Number page. It is used wherever a US TIN is required on a return or information return for a non-SSN-eligible individual. For a foreign contractor paid by a US company, the ITIN is often the piece that unlocks a treaty rate instead of full withholding.

Who Gets an ITIN

The IRS issues ITINs to individuals who “have a federal tax purpose and you’re not eligible for an SSN.” In practice that means foreign individuals with a US tax filing or reporting need who cannot obtain a Social Security Number. The most common situations for cross-border contractor work include:

• A non-US individual contractor claiming a reduced treaty rate that requires a US TIN
• A nonresident alien who must file Form 1040-NR because of US-source income
• Dependents or spouses of US citizens and resident aliens who are not SSN-eligible

An ITIN does not change the holder’s status outside the tax system. The IRS is explicit that an ITIN “doesn’t” qualify the holder for Social Security benefits or the Earned Income Tax Credit, “provide or change immigration status,” or “authorize you to work legally in the U.S.” It is “issued by the IRS for federal tax purposes only.”

How It Is Issued

The IRS issues the ITIN, and the applicant requests it on Form W-7, generally filed together with the federal tax return that creates the need. An applicant can submit the W-7 by mail, in person at an IRS Taxpayer Assistance Center that handles ITIN applications, or through an IRS-approved Certifying Acceptance Agent. The application has to include original documents or certified copies proving identity and foreign status. Once issued, the ITIN appears on the holder’s filings going forward, anywhere a US TIN is required.

ITINs and the W-8BEN Treaty Claim

The clearest reason a foreign contractor needs an ITIN is to claim treaty benefits on Form W-8BEN. The form has a dedicated field for the US tax ID. Line 5 of the current revision (Rev. October 2021) is labeled “U.S. taxpayer identification number (SSN or ITIN), if required.” A foreign individual who is not eligible for an SSN enters the ITIN there.

The treaty claim itself sits in Part II of the W-8BEN, where the contractor names the treaty country and the article and rate being claimed. A US TIN on line 5 is generally required to support that claim on most types of US-source income other than certain marketable securities. If a contractor leaves line 5 blank because they have no SSN and have not yet obtained an ITIN, the payer usually cannot honor the reduced rate and must withhold at the 30 percent statutory rate. Getting the ITIN is therefore the step that lets the treaty rate actually apply.

Common Mistakes

• Treating an ITIN as work authorization. It is for tax processing only. Work eligibility comes from immigration status, not the ITIN.
• Claiming a treaty rate with line 5 blank. Without the required US TIN on the W-8BEN, the payer defaults to 30 percent withholding even when the contractor would otherwise qualify for a treaty rate.
• Confusing it with an entity number. A business uses an EIN, not an ITIN. The ITIN is for individuals.

Related Terms

• EIN (Employer Identification Number): the entity equivalent, issued to businesses rather than individuals.
• Tax Residency Certificate (TRC): the residency proof a country issues to support a treaty or DTAA claim, separate from the US TIN itself.
• Form W-8BEN: carries the ITIN on line 5 to support a treaty claim in Part II.

Omnivoo Contract Management flags non-US contractors who need an ITIN to claim treaty benefits, tracks the application status, and applies the correct withholding rate while the number is pending.