Zamp Sales Tax API
The sales tax API that gets your returns filed
Calculate rooftop-accurate sales tax in real time across 12,000+ US jurisdictions and Canada, sync transactions for filing, and let Zamp’s tax team handle registrations, returns, and remittance. One REST API — and your API calls are never metered.
What is a sales tax API?
A sales tax API is a REST API that returns the exact sales tax to collect on a transaction, based on the delivery address and the taxability of each product. Instead of maintaining rate tables across 12,000+ US taxing jurisdictions — where state, county, city, and district rates stack and change constantly — your checkout, cart, or billing system sends the transaction to the API and gets the tax due back in real time. Most sales tax APIs stop at calculation. Zamp’s API connects directly to registrations, filings, and ongoing compliance: the same transactions you sync become the returns that Zamp’s tax team prepares, files, and remits on your behalf.What you can build
Every capability in the API
Calculations
Real-time sales tax calculation with a full jurisdiction-level breakdown on every transaction.
Transactions
Sync sales, refunds, and credit memos so Zamp can file and remit accurately.
Addresses
Address validation that normalizes ship-to addresses for rooftop-accurate rates.
Tax codes
Product tax codes that map your catalog to the right taxability rules.
Registrations
Your state registration footprint — where you’re registered as your nexus grows.
Filings
Filing history and status for the returns Zamp prepares and remits.
Companies
The legal entities and EINs associated with your API key.
Full API reference
Every endpoint, parameter, and response shape — with runnable examples.
Two ways to get started
Choose your path
Start with a free trial
Get a 30-day sandbox API key with all 47 remote-seller states preconfigured. No credit card, no sales call — make your first calculation in minutes.
Get a free trial key →Use your Zamp account
Production keys come with your Zamp account — alongside the managed service that registers, files, and remits for you. Copy your key and go.
Get production access →API or platform integration?
You don’t have to write code to use Zamp. Choose the path that fits your stack:Sales tax API FAQ
Do I need a credit card or a sales call to try the API?
Do I need a credit card or a sales call to try the API?
How accurate are the tax calculations?
How accurate are the tax calculations?
Does the API track economic nexus?
Does the API track economic nexus?
Does Zamp file the returns the API calculates?
Does Zamp file the returns the API calculates?
POST /calculations, persist the sale with POST /transactions, and Zamp’s tax team prepares, files, and remits the returns built from those transactions. Filing history is available through the Filings endpoint.How is Zamp's API different from calculation-only APIs?
How is Zamp's API different from calculation-only APIs?
How much does the API cost?
How much does the API cost?
Get started
Start collecting the right tax
Spin up a free trial key now — or talk to our team about bringing the fully managed service to your stack.