Every federal tax ID number format follows a fixed pattern that tells the IRS at a glance whether the number belongs to a person, a business, a foreign filer, an adopted child, or a paid preparer. Most are nine digits, but the hyphen placement, the allowable digit ranges, and in one case a leading letter make each type distinct. Knowing the correct layout helps you complete forms accurately, catch errors before a return is rejected, and recognize when a number on a document looks wrong.
Social Security Number
The SSN is nine digits split three-two-four by hyphens: XXX-XX-XXXX.1Social Security Administration. Social Security Numbers The first three digits are the area number, the middle two the group number, and the last four the serial number. Federal law requires the SSN on every tax return an individual files and on W-2s issued by employers.2Office of the Law Revision Counsel. 26 USC 6109 Identifying Numbers
Before June 25, 2011, the first three digits identified the state where the card was originally issued.3Social Security Administration. Meaning of the Social Security Number On that date the Social Security Administration switched to randomized assignment, and the area number no longer corresponds to any location.4Social Security Administration. Social Security Number Randomization Frequently Asked Questions Previously unused area numbers opened up under randomization, except 000, 666, and 900 through 999, which remain invalid. Advice about verifying an SSN by matching the area number to a state only applies to cards issued before mid-2011.
Employer Identification Number
Businesses, trusts, and estates use an EIN, which is also nine digits but hyphenated two-seven: XX-XXXXXXX.5Internal Revenue Service. Understanding Your EIN That split is the fastest way to tell an EIN from an SSN on paper. Trusts and estates use the identical format with no variations. The first two digits historically indicated the IRS campus or district that assigned the number.6Social Security Administration. RM 01103.015 – Composition of the Employer Identification Number (EIN)
Individual Taxpayer Identification Number
People who need to file a federal return but are not eligible for an SSN use an ITIN. It uses the same nine-digit, three-two-four hyphenated layout as an SSN with two built-in differences: the first digit is always 9, and the fourth and fifth digits fall within specific ranges — 50 through 65, 70 through 88, 90 through 92, or 94 through 99.7Internal Revenue Service. Individual Taxpayer Identification Number The shorthand form is 9XX-XX-XXXX, where the middle pair will never be something like 01 or 40.
An ITIN exists solely for federal tax purposes. It does not change immigration status, authorize work in the United States, or qualify anyone for Social Security benefits.8Internal Revenue Service. Individual Taxpayer Identification Number (ITIN) ITINs expire if not used on a return for three consecutive years, and the IRS retires blocks of middle-digit ranges on a rolling schedule.9Internal Revenue Service. Its Time Again for Folks to Renew Their ITINs – Here Are Some Things to Remember
Adoption Taxpayer Identification Number
When a child is placed in your home for a domestic adoption but doesn’t yet have an SSN, the IRS issues a temporary Adoption Taxpayer Identification Number so you can claim the child as a dependent.10Internal Revenue Service. Adoption Taxpayer Identification Number The ATIN is a nine-digit number in the standard hyphenated format. The IRS issues it for two years, with the option to request an extension if the adoption isn’t final by then. Once the child receives a permanent SSN, the ATIN is deactivated.
Preparer Taxpayer Identification Number
Paid tax preparers use a PTIN, which breaks from the all-numeric pattern. A PTIN is the letter P followed by eight digits, for example P12345678.11Legal Information Institute. Preparer Taxpayer Identification Number (PTIN) The P prefix makes the number instantly recognizable and keeps the preparer’s tracking identifier separate from any client’s personal information. Paid preparers must include the PTIN in the paid preparer section of every return they sign.12Internal Revenue Service. Frequently Asked Questions – Do I Need a PTIN
Truncated Taxpayer Identification Numbers
Many tax documents mailed to you show only the last four digits of your SSN or EIN, with the first five replaced by asterisks or Xs. That is a truncated taxpayer identification number, which the IRS allows on recipient copies (typically Copy B) as a privacy protection.13Internal Revenue Service. Truncated Taxpayer Identification Numbers The format looks like ***-**-1234 or XXX-XX-1234.
Truncation applies to SSNs, ITINs, EINs, and ATINs. You’ll see it on 1099 series forms, 1098 series forms, 1095-C forms, and 5498 series forms. Two places where truncation is never allowed: copies filed with the IRS itself (Copy A) and Forms W-2. A W-2 arriving with a truncated SSN is a sign something went wrong in processing.
Quick Reference
- SSN: XXX-XX-XXXX. Three-two-four, all numeric, used by individuals.
- EIN: XX-XXXXXXX. Two-seven, all numeric, used by businesses, trusts, and estates.
- ITIN: 9XX-XX-XXXX. Starts with 9, middle digits restricted to 50–65, 70–88, 90–92, or 94–99. Used by filers not eligible for an SSN.
- ATIN: Nine-digit temporary number in the standard three-two-four format. Used during a pending domestic adoption.
- PTIN: P followed by eight digits. Used by paid tax preparers.
- Truncated TIN: ***-**-XXXX or XXX-XX-XXXX. Last four digits only, used on recipient copies for privacy.
Why the Format Matters
A misplaced hyphen, a digit outside the valid range, or a number entered in the wrong field can cause the IRS to reject a return. If the format on a document you receive doesn’t match the pattern for its type, contact the issuing party before filing.