Tax Identification Numbers (TIN): SSN, ITIN, EIN, ATIN and PTIN
A tax identification number (TIN) is the number the IRS files your returns under. Individuals use a Social Security number (from the SSA, Form SS-5, free); people who must file but cannot get an SSN use an ITIN (Form W-7); businesses, estates and trusts use an EIN (free online, issued immediately); adopting parents can get a temporary ATIN (Form W-7A); paid preparers need a PTIN (IRS).
The five tax ID numbers at a glance
| Number | Who needs it | How to get it | Cost and timing | Expires? |
|---|---|---|---|---|
| SSN (Social Security number) | U.S. citizens and people authorized to work in the U.S. | Form SS-5 with proof of age, identity and citizenship or status, to the Social Security Administration | Free (IRS) | No |
| ITIN (individual taxpayer identification number) | Anyone with a federal tax purpose who is not eligible for an SSN: certain nonresident and resident aliens, their spouses and dependents. Nine digits, starts with 9 | Form W-7 with identity and foreign-status documents, usually attached to a tax return; by mail, at an IRS office or through an acceptance agent | Free; about 7 weeks, 9–11 weeks January 15–April 30 or from abroad (IRS) | Yes: December 31 after 3 tax years in a row without use on a federal return (IRS) |
| EIN (employer identification number) | Business entities, and estates and trusts with income reported on Form 1041 (IRS) | Online application, or Form SS-4 (IRS: About Form SS-4); a business whose principal place is outside the U.S. applies by phone, fax or mail (IRS) | Free; online EINs are issued immediately, one per responsible party per day (IRS) | No |
| ATIN (adoption taxpayer identification number) | Parents in a pending domestic adoption who cannot get the child’s SSN in time to file | Form W-7A with the placement documents | 4–8 weeks (IRS) | Deactivated after 2 years, or when the child’s SSN is reported |
| PTIN (preparer tax identification number) | Anyone paid to prepare federal returns | IRS online sign-up (about 15 minutes) or Form W-12 on paper (about 6 weeks) | $18.75, new or renewal; 2027 PTINs are being issued now (IRS) | Renewed every year |
An ITIN is for tax purposes only: it does not authorize work in the U.S., does not qualify you for Social Security benefits and does not change immigration status (IRS). The earned income credit cannot be claimed with an ITIN (IRS).
What a child’s number does to the credits
The child tax credit and its refundable part need the child’s SSN, valid for employment and issued before the return’s due date; a dependent with an ITIN or ATIN can get only the $500 credit for other dependents (IRS). The earned income credit counts a child only with a valid SSN (IRS). The same family, both parents with SSNs, computed both ways:
| Children with SSNs | Children with ITINs | |
|---|---|---|
| Nonrefundable credit (child tax credit / credit for other dependents) | $1,283 | $1,000 |
| Additional child tax credit (refundable) | $3,117 | $0 |
| Earned income credit | $4,396 | $0 |
| Federal tax owed | $0 | $283 |
| Difference in the family’s result | $7,796 | |
An estimate from QuantCalc’s open tax engine (federal 2.6.0, state 1.26.0) for the 2026 tax year. Not tax advice: your return depends on facts this page does not ask about, so check a move with your tax preparer or custodian before acting. How the engine computes each line, with its official source: federal, state.
Once the numbers are in place, plan the years after this return. QuantCalc runs savings, withdrawals and taxes year by year, free.
Run the free tax-aware simulation →Common questions
- What is a tax identification number?
- A TIN is the number the IRS uses to track your returns: a Social Security number issued by the Social Security Administration, or an ITIN, EIN, ATIN or PTIN issued by the IRS (IRS). Most individuals use their SSN; businesses, estates and trusts use an EIN.
- Is my Social Security number my tax ID number?
- Yes, for an individual who has one: the SSN is the TIN on your Form 1040, W-4 and W-9. People who cannot get an SSN but must file use an ITIN (IRS). Business entities, estates and trusts use an EIN.
- How do I get an EIN, and does it cost anything?
- Apply on the IRS website: it is free and, if approved, the EIN is issued online immediately. You can apply for one EIN per responsible party per day. The IRS warns about websites that charge for an EIN: “You never have to pay a fee for an EIN” (IRS).
- Do ITINs expire?
- Yes. An ITIN not used on a federal tax return for three consecutive tax years expires on December 31 after the third year. You renew it with Form W-7 only if it will be on a federal return (IRS).
- Can I get the child tax credit with an ITIN?
- Not for the child: each qualifying child needs an SSN valid for employment, issued before the return’s due date, and so does the taxpayer (or one spouse on a joint return). A dependent with an ITIN can qualify for the $500 credit for other dependents instead (IRS). In the example, the family’s refund is $7,796 smaller with ITINs.
Sources
- IRS: Taxpayer identification numbers (TIN)
- IRS: Individual Taxpayer Identification Number (ITIN)
- IRS: How to renew an ITIN
- IRS: Get an employer identification number
- IRS: About Form SS-4, Application for Employer Identification Number
- IRS: Adoption Taxpayer Identification Number (ATIN)
- IRS: PTIN requirements for tax return preparers
- IRS: Child tax credit
- IRS: Who qualifies for the earned income tax credit