NIF
Portugal
Portuguese taxpayer number (NIF) — 9 digits with an official check digit.
Validation Generation
Open source · MIT · .NET 10
Validate and Generate
Document Numbers in .NET
A modern .NET library for validating, generating and verifying document numbers across multiple countries using a clean and intuitive API.
14 document types · 13 generators · 4 countries
using DocumentNumber.Portugal.Vat.Validator;
var validator = new VatValidator();
if (validator.Validate("798945320"))
{
Console.WriteLine("Valid");
}Built for .NET developers
Everything you need to trust a document number before you store it.
Multiple document types
Validators and generators for Portugal, Spain, France, Brazil, IBAN and major payment card schemes.
Document validation
One call returns a clear result — format rules and check digits are handled for you.
Document generation
Produce structurally valid sample numbers for tests and demos — including check digits.
.NET Native
Pure managed libraries built on .NET Standard — drop them into any modern .NET application.
Clean API
A consistent Validate(value) and GenerateDocumentNumber() shape across every package.
Open Source
MIT licensed and developed in the open on GitHub — no hidden code, no vendor lock-in.
Extensible architecture
Program against the shared IDocumentNumberValidator abstraction and swap document types freely.
Production ready
Versioned on NuGet, covered by test suites and ready for real workloads.
Supported document types
Generated from the library catalogue — every card links to a live validator and, where available, a generator with runnable examples.
Portugal
NISS
Portugal
Portuguese social security number (NISS) — 11 digits with embedded check digits.
Validation Generation
Citizen Card
Portugal
Portuguese Citizen Card document number — 12 characters, digits plus a 3-letter series.
Validation Generation
NIB
Portugal
Portuguese bank account number (NIB) — 21 digits with bank check digits.
Validation Validation only
International
IBAN
International
International Bank Account Number — mod-97 checksum per ISO 13616.
Validation Generation
Spain
DNI / NIE / CIF
Spain
Spanish tax identifiers — DNI, NIE and CIF with their official check digits.
Validation Generation
France
TVA (VAT)
France
French VAT number (TVA) — SIREN-based with the official key check.
Validation Generation
Brazil
CPF / CNPJ
Brazil
Brazilian taxpayer identifiers — CPF (11 digits) and CNPJ (14 digits).
Validation Generation
Payment cards
American Express
International
American Express card numbers — 15 digits, 34/37 prefixes, Luhn check.
Validation Generation
Maestro
International
Maestro debit card numbers — 12 to 19 digits with Luhn check.
Validation Generation
Maestro UK
International
Maestro UK debit card numbers — 12 to 19 digits with Luhn check.
Validation Generation
Mastercard
International
Mastercard numbers — 16 digits, 51–55 and 2221–2720 ranges, Luhn check.
Validation Generation
VISA
International
Visa card numbers — 13, 16 or 19 digits starting with 4, Luhn check.
Validation Generation
VISA Electron
International
Visa Electron numbers — specific issuer ranges, 13 or 16 digits, Luhn check.
Validation Generation
Code examples
Real, copyable snippets — exactly what you write in your application.
using DocumentNumber.Portugal.Vat.Validator;
var validator = new VatValidator();
var isValid = validator.Validate("798945320");
Console.WriteLine(isValid ? "Valid" : "Invalid");using DocumentNumber.Portugal.Vat.Generator;
var generator = new VatGenerator();
var nif = generator.GenerateDocumentNumber();
Console.WriteLine(nif);using DocumentNumber.Portugal.Vat.Generator;
var generator = new VatGenerator();
var samples = Enumerable.Range(0, 5)
.Select(_ => generator.GenerateDocumentNumber())
.Distinct()
.ToArray();
Console.WriteLine($"{samples.Length} sample NIFs generated");using DocumentNumber.ValidatorAbstractions;
using DocumentNumber.Portugal.Vat.Validator;
IDocumentNumberValidator validator = new VatValidator();
var result = validator.Validate("798945320");
Console.WriteLine(result);Try it yourself
The same validation and generation power your .NET app gets — right here in the browser. No sign-up, nothing stored.
Library features
Small, focused packages that share one predictable design.
Validation Engine
Every validator applies the official format and check-digit rules for its document.
Number Generators
Random, valid samples on demand — ideal for test data, fixtures and demos.
Extensible Architecture
Small packages built on shared abstractions — take only what you need.
Country Specific Rules
Rules maintained per country for Portugal, Spain, France and Brazil.
High Quality Algorithms
Weighted, mod-97 and Luhn check-digit algorithms implemented to specification.
Easy Integration
One dotnet add package command and a single method call — that's it.
Get started
Install the package you need and validate your first document number in minutes.
1. Install
dotnet add package DocumentNumber.Portugal.Vat.Validator
dotnet add package DocumentNumber.Portugal.Niss.Validator
dotnet add package DocumentNumber.InternationalBankAccountNumber.ValidatorEvery document type ships as its own package — browse them all on NuGet.
2. Validate
using DocumentNumber.Portugal.Vat.Validator;
var validator = new VatValidator();
var isValid = validator.Validate("798945320");
Console.WriteLine(isValid ? "Valid" : "Invalid");Contributing
Document Number Validator is an open-source effort. New countries, new document types and better algorithms all start with a pull request.
Open Source MIT License Pull Requests Welcome
View on GitHub