Vat ID validator (EU and non-EU countries, with checksums)

Validate VAT numbers for European Union countries (and several other countries), with checksum verification.

Many libraries only check if a VAT number looks right (regex). vat_id_validator checks if it is right.

It verifies the checksum of the VAT number using country-specific algorithms (Luhn, Modulo 97, weighted sums, etc.). This means you can catch typos, transposed digits, and fake numbers instantly, without making a single network request to flaky government APIs like VIES.

Key Benefits

• ⚡ Instant & Offline: Zero network latency. No VIES downtime. Works everywhere.
• 🧮 Mathematical Verification: Catches invalid numbers that regex would pass (e.g., typos).
• 🛡️ Type-Safe Rust: Built for speed and reliability.
• 🌍 Multi-Country: Supports 30+ countries including EU, UK, Norway, Switzerland, Serbia, Russia, and Brazil.

🚀 Key Features

1. Explicit Country Validation

Don't guess! If you know the country, validate strictly against it.

// O(1) lookup - 2.3x faster than standard check!
let result = check_vat_by_country("GB999000005", "GB");

2. Serde Support

Enable the serde feature to serialize results straight to JSON.

{
  "value": "GB999000005",
  "is_valid": true,
  "is_valid_format": true,
  "is_supported_country": true,
  "country_name": "United Kingdom"
}

3. Country Identifier (GeoGuesser Mode)

Got a number but don't know where it's from?

use vat_id_validator::identify_country;

// Returns valid results for ALL matching countries
let matches = identify_country("999000005"); 

// Matches:
// - United Kingdom (it tries adding "GB" automatically!)
// - Any other country where "999000005" is valid

## Installation

Add this to your `Cargo.toml`:

```toml
[dependencies]
vat_id_validator = { version = "0.2.0", features = ["serde"] }

Usage

use vat_id_validator::check_vat;

fn main() {
    // Valid UK VAT number
    assert!(check_vat("GB999000005").is_valid);

    // Invalid format
    assert!(!check_vat("GB123").is_valid);

    // Valid format but invalid checksum
    assert!(!check_vat("GB999999974").is_valid);
}

🏎️ Benchmarks

We take "instant" seriously.

Measured on M-series Mac. Your mileage may vary, but it will be fast.

Supported Countries

• Andorra (AD)
• Austria (AT)
• Belgium (BE)
• Brazil (BR)
• Bulgaria (BG)
• Croatia (HR)
• Cyprus (CY)
• Czech Republic (CZ)
• Denmark (DK)
• Estonia (EE)
• Finland (FI)
• France (FR)
• Germany (DE)
• Greece (GR)
• Hungary (HU)
• Ireland (IE)
• Italy (IT)
• Latvia (LV)
• Lithuania (LT)
• Luxembourg (LU)
• Malta (MT)
• Netherlands (NL)
• Norway (NO)
• Poland (PL)
• Portugal (PT)
• Romania (RO)
• Russia (RU)
• Serbia (RS)
• Slovakia (SK)
• Slovenia (SI)
• Spain (ES)
• Sweden (SE)
• Switzerland (CH)
• United Kingdom (GB)

License

MIT / Apache-2.0