US Employer Identification Number (EIN) Regex for Go

What this pattern does

This page provides a well-structured, multi-part regular expression for matching us employer identification number (ein), ported and verified for Go. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// US Employer Identification Number (EIN)
// ReDoS-safe | RegexVault — Finance > Tax & Registration

package validation

import "regexp"

var usEmployerIdentificationNumberEinRe = regexp.MustCompile(`^(?:0[1-9]|[1-9][0-9])-[0-9]{7}$`)

func ValidateUsEmployerIdentificationNumberEin(s string) bool {
    return usEmployerIdentificationNumberEinRe.MatchString(s)
}

// Example
// fmt.Println(ValidateUsEmployerIdentificationNumberEin("12-3456789")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Tax & Registration category and carries a ReDoS-safe certification. That matters for Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

The first two digits identify the IRS campus that issued the EIN. 00 is not a valid prefix. EINs are the business equivalent of SSNs. Used on W-2, 1099, and other tax forms.