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Social Security Number (SSN): Federal Income Tax (2025 IRS Guide)

This guide covers “Social Security Number (SSN)” within federal income tax. The following material presents the IRS treatment of this topic, including the qualifications, exceptions, and examples in the source section. Read the rules alongside the facts of your own situation before deciding what to report, deduct, or document.

Adapted from Publication 17 (2025), Your Federal Income Tax, published by the Internal Revenue Service. This guide retains the source edition’s years, amounts, deadlines, and examples. It is guidance for that edition, not a statement that the same figures apply to every tax year.

Context for these rules

This section explains how to get ready to complete your tax return and when to report your income and expenses. It also explains how to complete certain sections of the form.

Social Security Number (SSN)

You must enter your SSN on your return. If you are married, enter the SSNs for both you and your spouse, whether you file jointly or separately.

If you are filing a joint return, include the SSNs in the same order as the names. Use this same order in submitting other forms and documents to the IRS.

.If you, or your spouse if filing jointly, don’t have an SSN (or ITIN) issued either on or on or before the due date of your 2025 return (including extensions), you can’t claim certain tax benefits on your original or an amended 2025 return..

Once you are issued an SSN, use it to file your tax return. Use your SSN to file your tax return even if your SSN does not authorize employment or if you have been issued an SSN that authorizes employment and you lose your employment authorization. An ITIN will not be issued to you once you have been issued an SSN. If you received your SSN after previously using an ITIN, stop using your ITIN. Use your SSN instead.

Check that both the name and SSN on your Form 1040 or 1040-SR, W-2, and 1099 agree with your social security card. If they don’t, certain deductions and credits on your Form 1040 or 1040-SR may be reduced or disallowed and you may not receive credit for your social security earnings. If your Form W-2 shows an incorrect SSN or name, notify your employer or the form-issuing agent as soon as possible to make sure your earnings are credited to your social security record. If the name or SSN on your social security card is incorrect, call the Social Security Administration (SSA) at 800-772-1213.

Name change.

If you changed your name because of marriage, divorce, etc., be sure to report the change to your local SSA office before filing your return. This prevents delays in processing your return and issuing refunds. It also safeguards your future social security benefits.

Dependent’s SSN.

You must provide the SSN of each dependent you claim, regardless of the dependent’s age. This requirement applies to all dependents (not just your children) claimed on your tax return.

.Your child must have an SSN valid for employment issued before the due date of your 2025 return (including extensions) to be considered a qualifying child for certain tax benefits on your original or amended 2025 return. See chapter 14..

Exception.

If your child was born and died in 2025 and didn’t have an SSN, enter “DIED” on row (3) of the Dependents section of Form 1040 or 1040-SR and include a copy of the child’s birth certificate, death certificate, or hospital records. The document must show that the child was born alive.

No SSN.

File Form SS-5, Application for a Social Security Card, with your local SSA office to get an SSN for yourself or your dependent. It usually takes about 2 weeks to get an SSN. If you or your dependent isn’t eligible for an SSN, see Individual taxpayer identification number (ITIN), later.

If you are a U.S. citizen or resident alien, you must show proof of age, identity, and citizenship or alien status with your Form SS-5. If you are 12 or older and have never been assigned an SSN, you must appear in person with this proof at an SSA office.

Form SS-5 is available at any SSA office, on the Internet at SSA.gov/forms/ss-5.pdf, or by calling 800-772-1213. If you have any questions about which documents you can use as proof of age, identity, or citizenship, contact your SSA office.

If your dependent doesn’t have an SSN by the time your return is due, you may want to ask for an extension of time to file, as explained earlier under When Do I Have To File.

If you don’t provide a required SSN or if you provide an incorrect SSN, your tax may be increased and any refund may be reduced.

Adoption taxpayer identification number (ATIN).

If you are in the process of adopting a child who is a U.S. citizen or resident and can’t get an SSN for the child until the adoption is final, you can apply for an ATIN to use instead of an SSN.

File Form W-7A, Application for Taxpayer Identification Number for Pending U.S. Adoptions, with the IRS to get an ATIN if all of the following are true.

  • You have a child living with you who was placed in your home for legal adoption.

  • You can’t get the child’s existing SSN even though you have made a reasonable attempt to get it from the birth parents, the placement agency, and other persons.

  • You can’t get an SSN for the child from the SSA because, for example, the adoption isn’t final.

  • You are eligible to claim the child as a dependent on your tax return.

After the adoption is final, you must apply for an SSN for the child. You can’t continue using the ATIN.

See Form W-7A for more information.

Nonresident alien spouse.

If your spouse is a nonresident alien, your spouse must have either an SSN or an ITIN if:

  • You file a joint return, or

  • Your spouse is filing a separate return.

If your spouse isn’t eligible for an SSN, see the following discussion on ITINs.

Individual taxpayer identification number (ITIN).

The IRS will issue you an ITIN if you are a nonresident or resident alien and you don’t have and aren’t eligible to get an SSN. This also applies to an alien spouse or dependent. To apply for an ITIN, file Form W-7 with the IRS. It usually takes about 7 weeks to get an ITIN. Enter the ITIN on your tax return wherever an SSN is requested.

Make sure your ITIN hasn’t expired. See Individual taxpayer identification number (ITIN) renewal, earlier, for more information on expiration and renewal of ITINs. You can also find more information at IRS.gov/ITIN.

.If you are applying for an ITIN for yourself, your spouse, or a dependent in order to file your tax return, attach your completed tax return to your Form W-7. See the Form W-7 instructions for how and where to file..

.You can’t e-file a return using an ITIN in the calendar year the ITIN is issued; however, you can e-file returns in the following years..

ITIN for tax use only.

An ITIN is for federal tax use only. It doesn’t entitle you to social security benefits or change your employment or immigration status under U.S. law.

Penalty for not providing social security number.

If you don’t include your SSN or the SSN of your spouse or dependent as required, you may have to pay a penalty. See the discussion on Penalties, later, for more information.

SSN on correspondence.

If you write to the IRS about your tax account, be sure to include your SSN (and the name and SSN of your spouse, if you filed a joint return) in your correspondence. Because your SSN is used to identify your account, this helps the IRS respond to your correspondence promptly.

Using the guidance

Keep the documents that establish the dates, amounts, and circumstances described above. References to other chapters, forms, worksheets, or earlier and later sections refer to the linked IRS publication. Check the full publication and its updates before relying on a rule for a different tax year or a situation not addressed here.

Sources and further reading

The cited U.S. government text is in the public domain. Source accessed October 28, 2026. Fynoptic has organized this material for educational use and is independent of, and not endorsed by, the IRS.

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