ITIN to SSN — how to retire your ITIN correctly

Once the Social Security Administration assigns you a Social Security number, your ITIN’s working life is over. IRS rules are direct on this point: you must use the SSN for all tax purposes from that day forward and stop using the ITIN. But the ITIN does not retire itself. You have to tell the IRS — in writing or in person — so the agency can void the ITIN and move every prior-year return, wage record, and withholding credit filed under it onto your new SSN. Skip this step and your tax history splits into two files that don’t talk to each other, which can cost you withholding credit and shrink future refunds. This page covers the exact letter to send, where it goes, and the credit-bureau step most people miss.

Why you cannot keep using the ITIN

The IRS states that “it is improper to use both the ITIN and the SSN assigned to the same person to file tax returns.” An ITIN exists only for people who are not eligible for an SSN — the moment you receive one (through a green card, work permit, or other status change), that eligibility condition disappears. If you keep filing under the ITIN, or alternate between the two numbers, the IRS warns you “may not receive credit for all wages paid and taxes withheld,” which can directly reduce any refund due. The two records must become one, and only the IRS can merge them. (If you’re unsure what your ITIN was for in the first place, see what an ITIN is.)

The letter that merges your records

You have two options: visit a local IRS Taxpayer Assistance Center, or write a letter. The letter route is simpler for most people. Per IRS instructions, send it to:

Internal Revenue Service Austin, TX 73301-0057

Note that this is not the same address where you mailed Form W-7 — the ITIN Operation box (P.O. Box 149342) handles applications, while the 73301-0057 address handles the merge correspondence.

Include in the letter:

  • Your complete name and mailing address
  • Your ITIN
  • A copy of your Social Security card
  • A copy of Notice CP565 (the ITIN assignment notice the IRS mailed when your ITIN was approved), if you still have it

Explain plainly that you have been assigned an SSN and want your tax records combined. Once processed, the IRS “will void the ITIN and associate all prior tax information filed under the ITIN with the SSN.” Your wage history, estimated payments, and withholding from ITIN years now live under the SSN.

What happens to the ITIN itself

The ITIN is voided — permanently. It is not transferred, suspended, or held in reserve. You cannot lend it to a family member, and you should never put it on a tax form, W-9, or bank document again. (Separately, any ITIN not used on a federal return for three consecutive tax years expires on its own, but don’t rely on passive expiration — the merge letter is what protects your filing history.)

Future returns, and fixing past ones

Every return you file after the SSN is issued goes under the SSN — including amended returns for years you originally filed with the ITIN. The Form 1040-X instructions tell filers to enter an ITIN only when they don’t have an SSN; once you have one, that’s the number that goes on the amended return. If, after the merge, you discover an ITIN-year return missed a credit you were eligible for, you can amend it under your SSN within the normal refund window. Be aware, though, that credits with their own SSN rules don’t open retroactively just because you have an SSN now — but going forward, the SSN can unlock credits the ITIN never could, including the Earned Income Tax Credit and (beginning with 2025 returns) the Child Tax Credit, which now requires the taxpayer to have an SSN. Compare your new position against which credits ITIN filers can and cannot claim.

The step most people miss: your credit file

If you built credit history under your ITIN — a secured card, an auto loan, an ITIN mortgage — that history is attached to the ITIN at Equifax, Experian, and TransUnion. The bureaus do not learn about your SSN automatically, and the IRS merge does nothing for your credit file. Industry guidance recommends notifying the IRS first, then writing to each of the three nationwide bureaus asking them to transfer your credit history from the ITIN to the SSN. Include copies of your ITIN documentation, your Social Security card, your immigration document (EAD or green card), and a recent utility bill or bank statement showing your name and current address. The transfer typically takes 30 to 60 days and should not affect your scores. Until it’s done, lenders pulling your SSN may see a thin or empty file even though you have years of on-time payments — see building credit with an ITIN for how that history was assembled in the first place.

Checklist

  1. Receive your Social Security card; stop using the ITIN immediately.
  2. Mail the merge letter (name, address, ITIN, SSN card copy, CP565 copy) to IRS, Austin, TX 73301-0057 — or visit a local IRS office.
  3. Update your SSN with your employer so Form W-2 reports wages correctly.
  4. Write to Equifax, Experian, and TransUnion to move your credit history to the SSN.
  5. File all future returns — and any amendments to ITIN-year returns — under the SSN only.

A family member who still files with an ITIN (a spouse or dependent without work authorization) keeps using theirs; the merge applies only to the person who received the SSN. For their renewals and paperwork, see how to apply for an ITIN.

Last verified: 2026-06-11. Sources: IRS — additional ITIN information, IRS — ITIN overview, IRS — Form 1040-X instructions.

General information — not legal or tax advice. For case-specific guidance, consult an Enrolled Agent or CPA with ITIN experience.