UEI Number Format: What a Valid Unique Entity ID Looks Like
The UEI number format explained: 12 alphanumeric characters, no O or I, never starting with zero. See valid UEI examples and how to validate one.
A valid Unique Entity ID (UEI) is exactly 12 characters long, made up of letters and digits with no dashes, spaces, or special characters. A typical UEI looks like ABC123DEF456. The format follows a few specific rules designed to keep it unambiguous and machine-readable across every federal system.
The UEI format rules
The government generates UEIs to a fixed specification:
- Length: exactly 12 characters.
- Character set: uppercase letters A–Z and digits 0–9 (alphanumeric).
- No special characters: no hyphens, spaces, periods, or slashes.
- First character is never zero (
0). This prevents leading-zero loss when a UEI is pasted into spreadsheets. - The letters
OandIare excluded to avoid confusion with the digits0and1. - No embedded meaning. Unlike some codes, the characters don't encode your location, size, or industry — it's a random, opaque identifier.
Valid UEI examples
These follow the rules and represent the shape of a real UEI (illustrative, not assigned):
ABC123DEF456R7K9M2P4Q8T6H3J5L8N1V4XZ
Invalid examples and why
| Value | Why it's invalid |
|---|---|
ABC123DEF45 | Only 11 characters (must be 12) |
0BC123DEF456 | Starts with a zero |
ABCI23DEF456 | Contains the letter I |
ABC-123-DEF4 | Contains hyphens |
ABC123DEF4560 | 13 characters (too long) |
How to validate a UEI quickly
You don't need special software. A UEI is valid in format if it:
- Has 12 characters total,
- Contains only A–Z and 0–9 (no
O, noI, no symbols), and - Doesn't start with
0.
Format validity only confirms the shape is correct — it does not confirm the UEI is real or active. To confirm an actual entity, do a UEI number lookup on SAM.gov.
UEI vs. DUNS format
The old DUNS number was 9 digits, numbers only (e.g., 123456789). The UEI is 12 alphanumeric characters. So a quick way to tell which identifier you're looking at: nine digits = legacy DUNS; twelve mixed letters and numbers = UEI. DUNS no longer has a federal role — see Unique Entity ID (UEI) explained for the full history.
UEI vs. CAGE code format
A CAGE code is 5 characters (alphanumeric) issued by the Defense Logistics Agency, while the UEI is 12 characters issued by SAM.gov. They're different identifiers for the same entity — your CAGE is assigned automatically alongside your UEI during registration. New to the difference? Start with what does UEI stand for.
Why the format matters in practice
Getting the format right prevents real problems:
- Spreadsheets: because a UEI can be all digits in places, store it as text, not a number, or trailing/leading characters can be mangled.
- Forms: enter all 12 characters with no spaces; partial UEIs fail validation on SAM.gov, Grants.gov, and contract forms.
- Capability statements and invoices: copy-paste rather than retype to avoid
O/0andI/1mix-ups (though the format rules make true ambiguity rare).
Frequently asked questions
How many characters is a UEI? Exactly 12 alphanumeric characters.
Does a UEI have letters or just numbers? Both — it's a mix of uppercase letters (A–Z, excluding O and I) and digits (0–9).
Can a UEI start with a zero?
No. The first character is never 0.
What's an example of a UEI number?
A UEI looks like ABC123DEF456 — 12 characters, no dashes.
Key takeaways
- A UEI is 12 alphanumeric characters, no symbols, never starting with
0, and excludesO/I. - It carries no embedded meaning — it's a random, permanent identifier.
- Store it as text to avoid spreadsheet corruption.
- Format-checking ≠ verification — confirm a real UEI via SAM.gov lookup.