API reference

One call gives the sales tax rate at a US street address, split into the state, county, city and district taxes that make it up. Every answer comes from the state's own published data; when that can't place an address in one rate, the API refuses with the reason instead of guessing.

GET /v1/rate

The rate at an address on a given day.

curl "https://api.opentaxrate.com/v1/rate?address=1410+E+Pine+St%2C+Seattle%2C+WA+98122" \
  -H "Authorization: Bearer otr_live_..."

Parameters

Give the address one of two ways. Both answer the same; with both, the fields win over the line.

GET /v1/rate?address=1410+E+Pine+St,+Seattle,+WA+98122

GET /v1/rate?state=WA&street=1410+E+Pine+St&city=Seattle&zip=98122

Response

{
  "state": "WA",
  "rate": 0.1055,
  "stateRate": 0.065,
  "localRate": 0.0405,
  "byType": {
    "general": 0.1055,
    "generalInterstate": 0.1055,
    "foodDrug": 0.1055,
    "foodDrugInterstate": 0.1055
  },
  "parts": [
    { "kind": "state", "name": "Washington", "code": "45:53", "rate": 0.065, "ids": {} },
    { "kind": "city", "name": "Seattle", "code": "01:63000", "rate": 0.0405, "ids": {} }
  ],
  "match": "street",
  "locationCode": "53-000-63000",
  "jurisdictions": "settled",
  "alternatives": [],
  "locationIds": { "Composite SER Code": "01726", "Location Code": "1726" },
  "zip4": "98109-4607",
  "source": "Streamlined Sales Tax files WAB2026Q4AUG27 + WAR2026Q4AUG27, street match on 2026-10-22",
  "reporting": {
    "agency": { "name": "Washington Department of Revenue", "url": "https://dor.wa.gov/..." },
    "form": "Combined Excise Tax Return",
    "notes": []
  }
}

Taxability

Name what was sold with code and the answer says whether that sale is taxed at the address on the date, at what rate, and the government page that says so. The general rate and parts don't change. Rules are researched for Washington, New York, California and every Canadian province and territory; everywhere else, and any code without a rule there, answers not_researched. See Taxability codes for the codes and what each covers.

GET /v1/rate?address=488+14th+St,+Brooklyn,+NY+11215&date=2026-10-08&code=food.catering,food.grocery

{
  "state": "NY",
  "rate": 0.08875,
  "parts": [
    { "kind": "state", "name": "New York", "code": "45:36", "rate": 0.04, "ids": {} },
    { "kind": "county", "name": "Kings", "code": "00:047", "rate": 0.04875, "ids": {} }
  ],
  ...
  "taxability": {
    "food.catering": {
      "treatment": "taxable",
      "rate": 0.08875,
      "taxes": [
        {
          "tax": "NY",
          "parts": ["45:36", "00:047"],
          "treatment": "taxable",
          "rate": 0.08875,
          "rule": {
            "summary": "A caterer's entire charge for a customer's event is taxable, including food, beverages, staff, rentals, room charges and service charges, even when separately stated.",
            "from": "2019-04-08",
            "fromIs": "earliest_verified",
            "treatment": "taxable",
            "conditions": [],
            "citations": [
              {
                "title": "TB-ST-110 (issued April 8, 2019)",
                "url": "https://www.tax.ny.gov/pubs_and_bulls/tg_bulletins/st/caterers_and_catering_services.htm"
              }
            ]
          }
        }
      ]
    },
    "food.grocery": {
      "treatment": "not_taxed",
      "rate": 0,
      "taxes": [
        {
          "tax": "NY",
          "parts": ["45:36", "00:047"],
          "treatment": "exempt",
          "rate": 0,
          "rule": { "summary": "Unprepared food for home consumption sold by food stores is exempt from state and local sales tax under Tax Law §1115(a)(1).", ... }
        }
      ]
    }
  }
}

Read each entry in three lines. When rate is null, never charge the general rate instead.

const t = answer.taxability[code];
if (t.rate !== null) charge(amount * t.rate);          // taxable, partial, not_taxed
else if (t.treatment === 'conditional') ask(t.taxes);  // show each rule's conditions; a person picks
else sendElsewhere();                                   // not_researched: never use the general rate

Errors

{ "error": "This address is within 12 m of a city line ...", "code": "ADDRESS_NEEDS_CONFIRMATION" }

GET /v1/coverage

Each state, how its addresses are placed, the files loaded for it, and its registered regionSources. See Sources for where each state's data comes from, or run the API yourself.

curl "https://api.opentaxrate.com/v1/coverage" \
  -H "Authorization: Bearer otr_live_..."