No federal tax ID is 11 digits. Every taxpayer identification number the IRS or Social Security Administration issues is exactly nine digits long, so a tax ID cannot be 11 digits in any federal context.1Cornell Law School Legal Information Institute (LII). Taxpayer Identification Number (TIN) If you are looking at an 11-character number and calling it a tax ID, you are almost certainly counting the dashes in a formatted SSN or EIN, looking at a state tax number, or holding a different kind of government identifier entirely.
Why an SSN or EIN Looks Like 11 Characters
Written out, a Social Security Number appears as XXX-XX-XXXX. Count every character on the page and you get 11: nine digits plus two hyphens. The hyphens are formatting, not part of the number. The same trick happens with an Employer Identification Number, which is printed XX-XXXXXXX. Ten characters on the page, nine digits in the number.
An Individual Taxpayer Identification Number follows the SSN format exactly (NNN-NN-NNNN) and always starts with a 9.2Internal Revenue Service. Taxpayer Identification Numbers (TIN) Nine digits, printed with two dashes, 11 characters on paper. Every federal taxpayer ID lands at nine digits when you strip the punctuation.
Numbers That Really Are Around 11 Characters
Plenty of legitimate government-issued numbers are longer than nine digits, and they get confused with federal tax IDs.
State tax identification numbers are the biggest source of mix-ups. States issue their own IDs for sales tax, unemployment insurance, and income tax withholding, and there is no uniform length. Depending on the state, a state tax ID can run anywhere from roughly 7 to 14 characters. An 11-character state number is entirely plausible, and someone seeing it on a state registration might reasonably assume it is a federal ID. It is not.
Other government identifiers add to the confusion. The Unique Entity Identifier (UEI) used in the federal contracting system at SAM.gov is a 12-character alphanumeric code that replaced the older 9-digit DUNS number. Internal IRS document locator numbers run 14 digits. Grant tracking numbers vary. None of these are taxpayer identification numbers, and none belong on a federal tax return in place of an SSN, ITIN, or EIN.
The Three Federal Tax IDs, and Their Actual Length
Social Security Number
Nine digits. The Social Security Administration issues the SSN to U.S. citizens and eligible resident aliens, and it is the default identifier for wage reporting and individual returns filed on Form 1040.2Internal Revenue Service. Taxpayer Identification Numbers (TIN)
Employer Identification Number
Nine digits. The EIN is the business equivalent of an SSN, required for corporations, partnerships, nonprofits, estates, and certain trusts to open bank accounts, hire employees, and file business returns.3Internal Revenue Service. Employer Identification Number
Individual Taxpayer Identification Number
Nine digits, always beginning with 9. The ITIN is issued to people who need to file a U.S. federal tax return but do not qualify for an SSN, including certain nonresident and resident aliens along with their spouses and dependents.2Internal Revenue Service. Taxpayer Identification Numbers (TIN) An ITIN is for federal tax filing only. It does not authorize work in the United States, does not create Social Security eligibility, and does not qualify anyone for the earned income credit.4Internal Revenue Service. Topic No. 857, Individual Taxpayer Identification Number (ITIN)
What About the PTIN?
The Preparer Tax Identification Number sometimes gets pulled into the 11-digit question. It is not 11 characters either. A PTIN is the letter “P” followed by eight digits, nine characters in total, such as P12345678.5Internal Revenue Service. IRM 3.21.264 IRS Individual Taxpayer Identification Number (ITIN)
Anyone paid to prepare federal tax returns is required to have a current PTIN, which is renewed each year.6Internal Revenue Service. Frequently Asked Questions – Do I Need a PTIN The renewal fee is $18.75 for the 2026 filing season.7Internal Revenue Service. PTIN Requirements for Tax Return Preparers The PTIN identifies the preparer on the return; it never replaces the taxpayer’s own SSN, ITIN, or EIN.
How to Figure Out What You Actually Have
If you are staring at a number and trying to identify it, count the digits, not the characters. Ignore hyphens, spaces, and any leading letter.
- Nine digits, formatted XXX-XX-XXXX, first digit is not 9: that is an SSN.
- Nine digits, formatted XXX-XX-XXXX, first digit is 9: that is an ITIN.
- Nine digits, formatted XX-XXXXXXX: that is an EIN.
- The letter P plus eight digits: that is a PTIN, and it belongs to a tax preparer, not the taxpayer.
- Anything longer or shorter than nine digits: it is not a federal tax ID. Most likely it is a state tax number, a UEI, an internal IRS reference number, or an unrelated government identifier.
Six digits is worth calling out for the same reason. The IRS Identity Protection PIN is a six-digit number tied to your account, not a tax ID, and it should be shared only with your tax preparer at filing time.8Internal Revenue Service. Get an Identity Protection PIN (IP PIN) If a form is asking for your “tax ID” and you are tempted to enter something with 11 digits, stop and check what number the form actually wants. On a federal return, the answer is nine digits every time.