The developer-friendly sales tax API and tax engine software built for high-growth platforms. Automate tax determination, rate calculations, and B2B exemptions anywhere in the world in under 50 milliseconds.
Generic tax lookup tools are too slow, hard to integrate, or unable to handle edge cases like digital product taxability, B2B reverse charges, or location-based exemptions.
One API covers every tax type, customer, and product you sell, with the reliability a production checkout needs.
One API handles every tax type. Quaderno calculates US state and local sales tax, EU and UK VAT, Canadian GST and HST, and Australian GST in real time based on your customer’s location.
Validate tax IDs at checkout, like EU VAT numbers through VIES or UK VAT numbers. When an ID is valid, Quaderno applies the reverse charge and zero-rates the transaction automatically.
SaaS, digital downloads, physical goods, and services are all taxed differently. Quaderno assigns the correct tax code to every line item, so you never overcharge or undercharge customers.
Built on redundant servers with a 99.99% uptime SLA. If a tax authority’s systems go down, Quaderno falls back on cached rate tables, so your checkout never fails or drops a sale.
Three steps to integrate real-time tax calculations.
Integrate fast with official client libraries for Node.js, Python, Ruby, PHP, and Go. Need more than calculations? The full Quaderno API also records transactions, sends invoices, and returns tax reports.
Test every checkout scenario with dedicated test keys before pushing code to production.
Subscribe to event notifications for tax updates, jurisdiction rule changes, and invoice creation.
Clear request parameters, complete code samples, and precise response schemas, ready for your engineering team.
We use Quaderno to automate tax calculations, generate compliant invoices at scale and track tax liabilities. The setup has been super easy and we were able to customise everything important to us. Their dashboard and reports are great and show all relevant information. The biggest benefit is the peace of mind that comes with using their service.
Sub-second tax calculations feed your entire global compliance workflow without extra code.
Track global sales volume, US economic nexus, and international VAT and GST registration thresholds in real time across 150+ countries.
Issue structured digital invoices and transmit real-time transaction data to tax authorities and the Peppol network across Europe.
Put tax returns on autopilot anywhere you sell. Download audit-ready reports or let Quaderno file directly on your behalf.
A sales tax engine, also called a tax determination engine or indirect tax engine, is software that works out the right sales tax, VAT, or GST for each transaction automatically. It combines the customer’s location, the product type, and the buyer’s tax status with an up-to-date database of tax rules and rates, then returns the tax to charge. Because sales tax determination happens inside your checkout or billing system, every sale is taxed correctly without manual lookups. Read our guide to how a tax engine works.
Quaderno Tax Engine is a real-time sales tax API for online businesses and platforms. It determines whether a sale is taxable, calculates the exact sales tax, VAT, or GST for the customer’s location and product type, and validates B2B tax IDs to apply the reverse charge, all in under 50 milliseconds. It’s part of the Quaderno platform, alongside Monitor, E-Invoicing, and Filing.
Quaderno calculates US state and local sales tax, EU and UK VAT, Canadian GST, HST, PST, and QST, and GST in Australia, New Zealand, India, and other countries through a single API. Rates are resolved from the customer’s location, down to full street addresses and 9-digit ZIP codes in the US. It works as a US sales tax API, a VAT API, and a GST API in one integration.
Yes. Every calculation returns the rate and the jurisdiction breakdown for the customer’s location. In the US, rates are resolved down to the full street address and 9-digit ZIP code, so customers in split tax jurisdictions get the right rate.
Yes. Quaderno validates EU VAT numbers through VIES and UK VAT numbers at checkout. When a B2B customer’s tax ID is valid, it applies the reverse charge and zero-rates the sale automatically. Learn how the reverse charge works in our EU VAT guide.
Yes. Quaderno is a REST sales tax API, so any checkout, including a custom React or headless build, can call it directly. Send the customer’s location and line items in one request and get back the tax rate, the amount, and the jurisdiction breakdown in under 50 milliseconds. The official SDKs are there if you want them, but they aren’t required. It’s sales tax calculation software your team integrates in hours, not months.
The API responds in under 50 milliseconds on average, so tax calculation never slows down your checkout. Quaderno runs on redundant servers with a 99.99% uptime SLA and falls back on cached rate tables if a tax authority’s systems are unavailable.
Look for three things: a response time that won’t slow your checkout, a free sandbox to test every scenario, and one integration for every tax you collect. Quaderno Tax Engine responds in under 50 milliseconds on average, includes a free sandbox with no time limit, ships official libraries for Node.js, Python, Ruby, PHP, and Go, and calculates US sales tax, EU and UK VAT, and GST through a single API.
Yes. The sandbox is free with no time limit and uses separate test API keys, so test calculations never touch your live data. Try every checkout scenario before going live. The API documentation includes code samples and complete request and response schemas.
Testing is free: the sandbox has no time limit, and every plan starts with a 7-day free trial. Plans are priced by monthly transaction volume, and API access, the sandbox, users, and integrations are included rather than sold as add-ons. No credit card is required. If you process more than 2,500 transactions a month, you can get a custom Enterprise plan. See all plans and prices.