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contix API vs EstimateTax API

Two free Finance APIs compared on access, reliability and developer ratings, using data from our daily health checks.

The verdict

  • Choose contix API if its data fits your use case better; on access and reliability it's level with EstimateTax API.
  • Choose EstimateTax API if its data fits your use case better; on access and reliability it's level with contix API.

Side by side

contix APIEstimateTax API
What it doesSpain: IBAN validation with bank and BIC, EU VAT number check (VIES), Modelo 303 VAT sums.US federal, state and local income tax calculation for 2026, with the source of every figure.
ProvidercontixEstimateTax
API keyNot neededNot needed
HTTPSYesYes
CORS (browser calls)YesYes
Status todayOnline · 746 msOnline · 873 ms
Uptime (30 days)UpUp
Developer ratingNot rated yetNot rated yet
PriceFree / free tierFree / free tier
contix docs ↗EstimateTax docs ↗

About each API

contix logocontix API

Spain: IBAN validation with bank and BIC, EU VAT number check (VIES), Modelo 303 VAT sums.

contix es API-first: todo lo que hace el panel web se puede hacer por API REST con un API-Key: crear clientes, emitir facturas Veri*factu con hash y QR, registrar cobros. Incluye servidor MCP para Claude, ChatGPT y Cursor. Sin coste adicional.

Strengths

  • No API key needed
  • Callable from the browser (CORS)
  • HTTPS

Ratings, reviews and FAQ →

EstimateTax logoEstimateTax API

US federal, state and local income tax calculation for 2026, with the source of every figure.

A REST API for US federal, state and local income tax calculation for 2026. Deterministic, source-attributed responses, no key required, 60 requests a minute.

Strengths

  • No API key needed
  • Callable from the browser (CORS)
  • HTTPS

Ratings, reviews and FAQ →

How to choose between them

  • Prototyping or a tutorial? Pick the one that needs no API key (both qualify).
  • Calling from a web page? You need CORS. Otherwise route requests through your own server or a serverless function.
  • Going to production? Favour HTTPS, a strong uptime record and a provider with clear rate limits and terms. Check each API's docs before you commit.
  • Still unsure? Both are free to try: send one request to each and compare the data you get back.

contix vs EstimateTax FAQ

Do contix API and EstimateTax API need an API key?

Neither needs an API key; you can call both straight away.

More comparisons

contix API alternatives · EstimateTax API alternatives · best Finance APIs