Build US sales tax into your systems

Headless access to Prophit's indirect tax engine. Calculate US sales and use tax with line-level rates, jurisdiction breakdowns, and nexus and exemption awareness — then record, void, and refund transactions and receive webhooks — from your checkout, billing, or ERP.

Explore Sales Tax API Sign in to the Developer Console

Commercial overview

Evaluating Prophit.ai for API-driven sales tax? Start with the Sales Tax API overview for buyer-focused positioning, then return here for endpoint reference, authentication, and sandbox setup.

What you can build

Calculate sales tax

Send a date, ship-to address, and lines; get line-level tax with a state/county/city/special breakdown, nexus and exemption awareness, freight and discount handling, and honest precision metadata.

Record transactions

Commit transactions, read them back by code, and run the full lifecycle — void and full or partial refunds — with sandbox traffic isolated from filing, nexus, and production reporting.

Operate with confidence

Manage keys with one-time secret reveal and rotation, watch request logs and usage, and subscribe HMAC-signed webhooks with automatic retries — all from the Developer Console.

Quickstart

After workspace enablement, create a sandbox key and make a stateless reference calculation:

Full quickstart →

curl -X POST https://prophit.ai/api/v1/tax/calculate \
  -H "Authorization: Bearer itms_test_YOUR_SANDBOX_KEY" \
  -H "Content-Type: application/json" \
  -d '{
	    "transaction_date": "2026-07-15",
	    "nexus_mode": "reference",
	    "ship_to": {
	      "line1": "350 5th Ave",
	      "city": "New York",
	      "state": "NY",
	      "zip_code": "10118"
	    },
	    "lines": [
	      { "number": 1, "amount": "100.00", "quantity": 1, "tax_code": "TAXABLE", "description": "Tangible personal property test item" }
    ]
  }'

The API is versioned under /api/v1, authenticated with API keys, and scoped to your organization, location, and environment. United States sales and use tax, USD.

Documentation

QuickstartGet a sandbox key and make your first tax calculation.UI workflow mapMap product screens and operator actions to API operations, evidence, and authority boundaries.AuthenticationAPI keys, prefixes, one-time secrets, rotation.EnvironmentsSandbox vs live, isolation, and live-access enablement.CoverageDiscover current jurisdiction coverage and calculation authority at runtime.Service providersOnboard taxpayer clients, select tenant context, and prepare portfolio return output.Endpoint referenceEvery /api/v1 endpoint with method, scope, and behavior.Rate limitsRequest buckets, batch limits, retention, and safe retry behavior.SchemasRequest and response fields, metadata, and warnings.ErrorsError envelope, codes, request IDs, validation.WebhooksEvents, signing, retries, replay, and verification.Transaction lifecycleCalculate, commit, void, refund, adjust, credit, and duplicates.Migrate from AvaTaxMap AvaTax connection, transaction, field, and retry behavior to ITMS.Code samplescURL, JavaScript, Python, Node helper, webhook verify.ChangelogCustomer-visible API contract changes, compatibility notes, and deprecations.

Test in a safe sandbox

Sandbox access is manually enabled. Once approved, run the quickstart against supported deterministic tax content and review the authority returned for each calculation.

Before you buy, inspect the difficult cases.

Missing product identity. Certificate dates. Partial refunds. Retries. Open the inputs, executed reference results and limitations.

Inspect the evidence →

Production standalone Sales Tax and Use Tax Engine module subscriptions ($99/month per location through sales-assisted setup, with 10,000 calls/month included) return determinations to source systems through an API. These module prices do not quote pay-for-use task charges.
Module-based subscriptions: $199/month Starter and $599/month Professional per organization, with no additional per-state, per-filing or per-transaction fees for included usage. User, location, transaction and certificate allowances apply. These prices and the separate module menu are not pay-for-use task rates.