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Data source attribution

Version 1.0 · Last updated 2026-10-08 · Previous versions: none

In short

Address geocoding uses open data that requires credit. This page gives that credit: OpenStreetMap, GeoNames, OpenAddresses sources and the U.S. Census Bureau, plus a USPS notice.

1. Geocoding data

We use Geocodio to turn addresses into coordinates; we then match them to tax boundaries. Geocodio does not ask for credit itself, but it builds on open datasets whose licences do, so we credit those below.

2. OpenStreetMap

© OpenStreetMap contributors. Data available under the Open Database Licence (ODbL). openstreetmap.org/copyright

3. GeoNames

Place-name data from GeoNames, licensed under CC BY 4.0.

4. OpenAddresses

Address data from OpenAddresses contributors. The sources below require attribution or are published under a CC BY licence. The list is taken from the OpenAddresses source registry (263 sources, fetched 2026-10-09); we err on the side of crediting too many rather than too few.

Show the 263 credited sources

5. United States Postal Service

The price of our service is neither established, controlled or approved by the United States Postal Service. Asizor advertising is neither approved nor endorsed by the United States Postal Service®.

6. U.S. Census Bureau

Boundary and reference data come from the U.S. Census Bureau (TIGER/Line and the Census Geocoder). These are public domain; we credit them as a courtesy.

7. Tax data

Tax rates come from state and local government publications. Every number in an API response carries its own source URL and effective dates. See coverage.