Washington State Sales Tax Calculation library

washington-state-sales-tax on NPM

This is a very simple library to calculate sales tax rates for Washington State, in the United States. It doesn't do anything else.

Useful if your only nexus is in Washington state. I take no responsibility for your use of this library (see license). API is unofficially modeled after TaxJar (no affiliation, this is what I was replacing). Nice product which also prepares your filing for you (for a fee), and handles more complex tax scenarios.

Tax Rates valid for Jan 01 2023 to Oct 01 2024.

How it works

Named tax rates by city

If a named tax rate is provided by Washington State via https://dor.wa.gov/get-form-or-publication/publications-subject/local-sales-use-tax-rates-excel-format, this rate is returned. See the example below.

County lookup via Mapquest Open APIs

If a rate for a city is not explicitly provided, it is charged the county unincorporated rate.

To determine this, we need to first determine which county a city is in.

For this, we are using the Mapquest Open API. https://developer.mapquest.com/documentation/open/

This now requires registration via https://developer.mapquest.com/documentation/

Inferred tax rate

If you choose not to use the Mapquest API or it returns an error, and the city rate is not explicity provided in the dataset above, a rate of 10.25% is charged, and the result will include the key/value inferred = true. It is up to you how you wish to implement this and you take responsibility for how you handle this fallback case (for example, you may refund this manually or set up a system to alert your customer in case this occurs).

Installation

npm i -s washington-state-sales-tax

Usage

Require: const { taxForOrder } = require('washington-state-sales-tax');

The function taxForOrder takes two arguments, a parameters object, which should have two keys: amount and zip. The second argument is a callback function, with one argument, a resulting output object.

You can see how it works in test.js

taxForOrder({
    amount: 100,
    zip: 98101
}, function (data) {
    console.log(data);
});

Expected output

{
  "amount": 100,
  "shipping": 0,
  "order_total_amount": 100,
  "zip": "98101",
  "latitude": 47.6114,
  "longitude": -122.3305,
  "city": "Seattle",
  "state": "WA",
  "country": "US",
  "tax_source": "destination",
  "taxable_amount": 100,
  "freight_taxable": true,
  "has_nexus": true,
  "county": "King",
  "locationCode": 1726,
  "localTaxRate": 0.036,
  "stateTaxRate": 0.065,
  "totalTaxRate": 0.101,
  "taxLocaleString": "Seattle",
  "jurisdictions": {
    "country": "US",
    "state": "WA",
    "county": "KING",
    "city": "SEATTLE"
  },
  "rate": 0.101,
  "inferred": false,
  "amount_to_collect": 10.1
}

Example: An out-of-state zip code is provided

// 10001 Manhattan, New York City, NY – Out of state (no tax collected)
taxForOrder({
    amount: 100,
    zip: 10001
}, function (data) {
    console.log(data);
});

Result

{
  "amount": 100,
  "shipping": 0,
  "order_total_amount": 100,
  "zip": "10001",
  "latitude": 40.7484,
  "longitude": -73.9967,
  "city": "New York",
  "state": "NY",
  "country": "US",
  "freight_taxable": true,
  "amount_to_collect": 0,
  "taxable_amount": 0,
  "has_nexus": false,
  "rate": 0
}

Example: Tax applicable but rate is not determined, and an inferred tax rate is used

// Outlook, WA 98938 - Yakima County Unincorp. Areas - Inferred tax rate
taxForOrder({
    amount: 100,
    zip: 98938
}, function (data) {
    console.log(data);
});

Result

{
  "amount": 100,
  "shipping": 0,
  "order_total_amount": 100,
  "zip": "98938",
  "latitude": 46.3525,
  "longitude": -120.097,
  "city": "Outlook",
  "state": "WA",
  "country": "US",
  "tax_source": "destination",
  "taxable_amount": 100,
  "freight_taxable": true,
  "has_nexus": true,
  "jurisdictions": {
    "country": "US",
    "state": "WA",
    "city": "OUTLOOK"
  },
  "inferredRate": 0.101,
  "inferred": true,
  "rate": 0.101,
  "amount_to_collect": 10.1
}

Tests

You can run some basic tests from the command line via npm test. This is also a great way to see how it works & kick the tires a bit, by editing test.js. Make sure you understand what this library does before you use it, as there may be financial or legal consequences for collecting taxes incorrectly.

Maintained by Meeting Room 365

This library is maintained (unofficially) by the team that builds Meeting Room 365 – The Fastest Way to add a Meeting Room Display to Office 365, Exchange, and Google Workspace. Check us out!