From ITIN to Social Security number: what to update and what to reclaim

You cannot hold an ITIN and a Social Security number at the same time, and the IRS does not join the two records up on its own. Until you tell it, wages and withholding reported under the old number may never be credited to you.

Stop using the ITIN

From the day the Social Security number is issued, that is the number you use for tax purposes and the ITIN is finished with. In practice it goes on your next return, on a fresh Form W-4 for your employer, on the forms your bank asks you to complete, and on anything else that asks for a taxpayer identification number.

Tell the IRS, and how

Holding the number is not the same as the IRS knowing you hold it. Notify the agency and it brings the records kept under both numbers together. Leave it undone and you may not be credited for all the wages paid to you and all the tax withheld, which can shrink a refund that was yours.

There are two routes: by post, or in person at a local IRS office. The letter itself is short. State that a Social Security number has been assigned to you and that you want your tax records combined, and enclose your full name, your mailing address, your ITIN together with a copy of the assignment notice if you still have it, and a copy of your Social Security card. The address it goes to is printed on the IRS ITIN page.

The IRS describes what happens next plainly enough: the ITIN is voided, and the tax information previously filed under it is attached instead to the Social Security number.

Update the employer, not just the IRS

The step people skip is the employer. Give the new number over so that future wage reporting carries it, then check what actually appears on the next pay stub or wage statement rather than assuming it went through. A wage statement already issued under the old number is the employer's to fix, on a corrected wage statement, and not yours. Nothing was wrong about issuing it, either: an ITIN was the number you had at the time, and the correction exists so that the wages follow you across to the new one. Form W-2 covers what those statements say.

What opens up, and from when

Several credits ask for a Social Security number rather than an ITIN, so holding one changes what a future return is able to claim. Filing with an ITIN sets out which credits an ITIN reaches and which it does not, and that list is not repeated here.

One rule has to be stated exactly, because it is what readers most often ask. Where a Social Security number was missing from a return because you or your spouse did not hold a valid one by that year's due date, extensions included, and the number only arrived afterwards, you cannot go back and amend that year to claim the earned income credit.

The exception travels with the rule. If a number had already been issued but was not valid for the credit, and by that same due date you or your spouse had become eligible for a card that does not carry the "Not valid for employment" legend, then the credit can be claimed for that year on an original or an amended return, even where the card itself had not been updated in time. So where a card carries the legend and immigration status has since changed, ask the Social Security Administration for a card without it. The earned income credit covers the rest of the credit's conditions.

Which years are still worth amending

A refund cannot be claimed indefinitely. A claim on Form 1040-X has to be filed within 3 years of the date you filed the original return, or within two years of the date you paid the tax, whichever of those falls later, and a return sent in ahead of the due date counts as having been filed on the due date itself.

For this reader that narrows the search. The years still inside the window are worth checking for anything that did not depend on holding a Social Security number by the old due date, and the earned income credit is not one of those things. Form 1040-X covers how an amended return is put together, and checking a refund, an amended return or a payment covers how to follow it once it is sent.

What does not change

A new Social Security number does not by itself change your immigration status, your residency for tax purposes, or which filing status is open to you, and it does not reopen a year whose refund window has already closed. In a household where some members still hold ITINs, each credit is still tested person by person, which filing with an ITIN works through. Keep the ITIN assignment notice and a copy of the letter you sent, with the date it went, so that you can show what you did if a later year's wages or withholding fail to line up.