# Is there an API for sales tax rates by address?

> Is there an API for US sales tax rates by address?

Not from the states as a lookup service: the Streamlined Sales Tax (SST) member states each publish a [rate file and a boundary file](https://www.streamlinedsalestax.org/Shared-Pages/rate-and-boundary-files) to download, and you match an address or ZIP+4 to its jurisdictions and add up their rates yourself. The Olympus US Sales Tax Rates API does that lookup: `GET /v1/sales-tax/rates/address` returns the published state, county, city and special district rates for a street address in the states it has published, with effective dates and the file each rate came from. It is a rate lookup, not a tax calculation.

## The official route, and what it lacks

Under the Streamlined Sales and Use Tax Agreement, "Each Streamlined Member State is required to provide a rate file and a boundary file." The boundary file "generally identifies the tax codes (for each taxing jurisdiction) that apply to an address based on either the 5 or 9-digit zip code", and for some states on the actual address; the rate file "provides the rates that apply to each tax code." The SST lists 23 full member states and one associate member (Tennessee); states outside the agreement, such as Texas, California, New York and Florida, publish their rates in their own formats.

What that leaves to you: downloading each state's files as they change, matching addresses to address ranges or ZIP+4 records, and handling effective dates. A 5-digit ZIP is not enough on its own: the Washington Department of Revenue warns that "5-digit ZIP codes do not accurately correspond with tax rates or taxing jurisdictions."

## What the US Sales Tax Rates API serves

Published sales and use tax rates by jurisdiction (state, county, city, special district) for Streamlined Sales Tax member states and for states served from their revenue department's own files, by street address, ZIP+4 or 5-digit ZIP, with effective dates.

### Limits

- Not a tax calculation or taxability determination: sourcing, nexus, exemptions and product taxability change what is owed.
- A 5-digit ZIP that spans several jurisdiction sets is answered as ambiguous with every candidate; no single rate is chosen.
- Lookups always answer 200 with status matched, ambiguous, unmatched or unsupported.
- Every answer carries source (sst_files, state_revenue_files, census_boundaries, statewide) and accuracy (address, zip4, zip5, county, state); census_boundaries means the county comes from Census, the rate from the state.

**Not included:** transaction tax calculation; states not listed as published (e.g. CA, TX, NY, FL); special rates (meals, lodging, rentals); taxability rules; filing or remittance.

Published states today: CT, DC, GA, IA, IL, IN, KY, MA, MD, ME, MI, MN, ND, NE, NJ, NV, OH, OK, PA, RI, SD, TN, UT, VT, WI, WV, WY. Every other state is answered as `unsupported`, with no rate.

## Example request and response

Rates for a street address (1819 Farnam St, Omaha, Nebraska):

Request:

```sh
curl -s "https://api.olympus.new-odyssey.com/v1/sales-tax/rates/address?street=1819+Farnam+St&city=Omaha&state=NE&zip=68183" \
  -H "X-API-Key: $OLYMPUS_API_KEY"
```

200 OK (abridged):

```json
{
  "data": {
    "status": "matched",
    "reason": null,
    "date": "…",
    "match": { "method": "address_range", "confidence": "high", "attempted": ["address_range"] },
    "combined_rates": { "general_intrastate": …, "general_interstate": … },
    "candidates": [
      {
        "state_code": "NE",
        "source": "sst_files",
        "accuracy": "address",
        "complete": true,
        "jurisdictions": [
          { "level": "state", "code": "…", "name": "…", "rates": …, "effective_from": "…", "provenance": … },
          { "level": "city", "code": "…", "name": "…", "fips": "…", "rates": …, "effective_from": "…", "provenance": … }
        ],
        "boundary": { "record_type": "A", "source": "sst_boundary_file", "effective_from": "…", "provenance": … }
      }
    ]
  },
  "meta": {
    "datasets": [{ "dataset_id": "…", "freshness": "fresh" }],
    "notices": [
      { "code": "not_a_taxability_determination", "message": "…" },
      { "code": "source_not_certified", "message": "…" }
    ]
  }
}
```

Every lookup answers 200 with a `status`: `matched`, `ambiguous` (a 5-digit ZIP that spans several jurisdiction sets, with every candidate), `unmatched` or `unsupported` (a state that is not published, with no rate). `GET /v1/sales-tax/rates/zip/{zip}` takes a ZIP+4 or 5-digit ZIP, and `date` returns the rates in force on another day.

## Coverage and refresh

**Coverage:** Only the states Olympus has published: SST member states (from SST files) and states served from their revenue department's own sources (source and accuracy are on every answer). GET /v1/sales-tax/coverage is the authority: it lists them and their dates, and published_states is a copy of it. Every other state is answered as unsupported, with no rate.

- The latest SST rate and boundary files of each state (e.g. 2026 Q4); the file name is returned with every rate.
- Dates from five years before a state's latest file quarter to its end; dates outside that range are unsupported.

**Refresh:** Checked on the 2nd and 16th of each month (stale after 100 days). `GET /v1/sales-tax/coverage` lists exactly what is loaded right now.

## Price

Every Olympus plan includes the US Sales Tax Rates API and every other live API. The Free plan (no card) gives 1,000 requests a month to each live API at 10 requests a minute. Paid plans: Developer $79 a month (50,000 requests per API), Growth $299 a month (250,000 requests per API), Business $999 a month (1,000,000 requests per API); Enterprise from $2,500 a month on request. Prices in USD; see [pricing](https://olympus.new-odyssey.com/pricing) for rate limits and what counts as a request.

## Docs

- [US Sales Tax Rates API](https://olympus.new-odyssey.com/apis/sales-tax): what it serves and its endpoints
- [API reference](https://olympus.new-odyssey.com/docs/sales-tax); OpenAPI contract at `/openapi/sales-tax.yaml`
- [Coverage and known limits](https://olympus.new-odyssey.com/coverage#sales-tax)
- [How sales tax rates by address work](https://olympus.new-odyssey.com/guides/sales-tax-rates-by-address)
- [Can you look up sales tax by ZIP code?](https://olympus.new-odyssey.com/answers/sales-tax-by-zip-code)
- [Get a free API key](https://olympus.new-odyssey.com/signup), then send it in the `X-API-Key` header
- From an AI agent: the [MCP server](https://olympus.new-odyssey.com/agents) tools `lookup_us_sales_tax` and `get_product_coverage`

## Questions

### Is there a free sales tax rate API?

The SST rate and boundary files are free to download but are files, not an API. The Olympus Free plan includes 1,000 rate lookups a month, with no card.

### Does it calculate the tax on a sale?

No. It returns published rates. Sourcing rules, nexus, exemptions and product taxability change what is owed; for calculation, SST states certify Certified Service Providers.

### Which states are covered?

The states Olympus has published (CT, DC, GA, IA, IL, IN, KY, MA, MD, ME, MI, MN, ND, NE, NJ, NV, OH, OK, PA, RI, SD, TN, UT, VT, WI, WV, WY); `GET /v1/sales-tax/coverage` is the authoritative list. California, Texas, New York and Florida are not covered.

### Can I look up a rate by ZIP code?

Yes, by ZIP+4 or 5-digit ZIP. A 5-digit ZIP that spans several jurisdiction sets is answered as `ambiguous`, with every candidate, rather than one guessed rate.

## Sources

- Streamlined Sales Tax Governing Board: [Rate and boundary files](https://www.streamlinedsalestax.org/Shared-Pages/rate-and-boundary-files)
- Streamlined Sales Tax Governing Board: [FAQs about Streamlined](https://www.streamlinedsalestax.org/Shared-Pages/faqs/faqs---about-streamlined)
- Washington State Department of Revenue: [Information for online sellers using shopping carts](https://dor.wa.gov/information-transitioning-destination-based-sales-tax-online-sellers-using-shopping-carts)

## Related

- [US Sales Tax Rates API](https://olympus.new-odyssey.com/apis/sales-tax)
- [Sales Tax Rates API reference](https://olympus.new-odyssey.com/docs/sales-tax)
- [Sales tax rates by address, explained](https://olympus.new-odyssey.com/guides/sales-tax-rates-by-address)
- [Can you look up sales tax by ZIP code?](https://olympus.new-odyssey.com/answers/sales-tax-by-zip-code)

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Published 2026-10-24, updated 2026-10-24 by New Odyssey. Canonical: https://olympus.new-odyssey.com/answers/sales-tax-rate-api