Regex for US EIN
Employer Identification Number, 9 digits XX-XXXXXXX.
The pattern
^\d{2}-\d{7}$
What it matches
12-345678999-0000001
What it doesn't match
12345678912-3456781-2345678
Notes & gotchas
EIN format is two digits, dash, seven digits. The first two digits are the IRS campus code. Some sources reject specific prefixes (00, 07, 08, 09, 17, 18, 19, 28, 29, 49, 78, 79, 89) but the strict list changes.
Code in your language
Use the explainer's Code tab to generate ready-to-paste snippets in JavaScript, Python, Java, .NET, Go, Ruby, and PHP for this pattern.
Open in explainer →About this pattern
US-specific identifiers follow patterns set by federal and state authorities (SSA, IRS, USPS, state DMVs). Regex catches malformed values; final validation usually requires an authoritative lookup.
Quick usage in different languages
Once you've validated a candidate value matches this pattern, you'll typically use it inside your application code. Each language has its own regex syntax:
- JavaScript:
new RegExp(pattern).test(value) - Python:
re.match(pattern, value)with raw strings:r"pattern" - Java:
Pattern.compile(pattern).matcher(value).matches() - C# / .NET:
Regex.IsMatch(value, pattern) - Go:
regexp.MustCompile(pattern).MatchString(value)— Go uses RE2 so some advanced features aren't available - Ruby:
value =~ /pattern/orpattern.match?(value) - PHP:
preg_match('/pattern/', $value)
The explainer's Code tab generates these for any pattern you paste — including the right escaping and idioms for each language.
Common pitfalls
- Anchors matter. If the pattern uses
^and$it expects the entire input to match. To find this pattern inside a longer text, remove the anchors and use the/gflag. - Case sensitivity. Letter ranges like
[A-Z]only match uppercase. Use theiflag or[A-Za-z]for case-insensitive matching. - Escape user input. If you're building a regex from a string variable, escape regex metacharacters first to avoid bugs or injection.
- Performance. For this specific pattern the risk is low, but be cautious of nested quantifiers when adapting it — they can cause exponential backtracking on adversarial input.
See also
Browse all 300 patterns in the library, or open this regex in the interactive explainer for a token-by-token breakdown, live testing, and code in seven languages.
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