Documentation
The API is one endpoint and three ideas: a rate, two honesty flags, and a date you can wind back.
Authenticate
Every request carries a key as a bearer token. Create one in the portal.
Authorization: Bearer situs_live_...
Keys beginning situs_test_ work the same way and are meant for
your own test suite. A revoked key stops working within a minute: the API
holds a verified key for 60 seconds, and for up to 5 minutes if the account
portal is unreachable, so that a blip here does not lock everyone out.
Look up a rate
GET https://api.situs.tax/v1/rate?address=...&state=CA GET https://api.situs.tax/v1/rate?state=CA&zip=95814
Pass an address for an address-level answer. Pass a state and ZIP when that
is all you have, and read precision to know which rung you
landed on.
Read the flags
| Field | Values | Means |
|---|---|---|
| precision | address, zip, city, county, state |
Which rung of the ladder answered. address means the
address was placed inside real jurisdiction boundaries.
city and county mean a named district
matched. zip and state are fallbacks:
state means no more specific match was found, so the
state base rate came back. Read coverage before
you trust it — a state answer may be the
whole rate or may be a floor, and precision alone cannot
tell you which.
|
| coverage | exact, approximate |
Whether the rate is the whole answer.
exact means every district that can tax that point is in
our data. approximate means a locality there can require
a remote seller to collect and we could not place the address inside
it, so the rate is a floor and can only be too low.
New Jersey at 6.625% is exact: no locality in the state
levies a sales tax. Colorado at 2.9% is approximate, and
short by roughly five points, because its home-rule cities publish no
usable dataset. Both answer with
precision: "state", so this is the only field that tells
them apart.
|
Replay a past date
GET https://api.situs.tax/v1/rate?state=CA&zip=95814&date=2026-03-14
Returns the rate that was in force on that day. Rate versions are additive and never overwritten, so this keeps answering for dates in the past indefinitely. This is the field an auditor asks about.
Full reference
The complete reference, including error shapes and rate limits, lives with the API: https://api.situs.tax/docs.
Plugins
WooCommerce, Shopify and WordPress plugins that call this API are planned. If you want one sooner than the others, say which.