Interest Rate (APR / APY) Regex for Go

What this pattern does

This page provides a well-structured, multi-part regular expression for matching interest rate (apr / apy), 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

// Interest Rate (APR / APY)
// ReDoS-safe | RegexVault — Finance > Currency & Money

package validation

import "regexp"

var interestRateAprApyRe = regexp.MustCompile(`^(?:0(?:\.[0-9]{1,4})?|[1-9][0-9]{0,4}(?:\.[0-9]{1,4})?)%?$`)

func ValidateInterestRateAprApy(s string) bool {
    return interestRateAprApyRe.MatchString(s)
}

// Example
// fmt.Println(ValidateInterestRateAprApy("0")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Currency & Money 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

Does not impose an upper bound to accommodate DeFi yields, payday loan rates, or penalty rates that can exceed 100%. Add a domain-specific cap at the application level. APR and APY differ when compounding is applied.