From Tax Rates Wiki
Geolocation is Avalara's process of creating unprecedented rooftop-level accuracy for sales tax rates with the following techniques:
- Mapping jurisdiction boundaries precisely using latitude and longitude
- Constantly updating a proprietary database with the latest rate and taxability rules
- Combining our jurisdiction and rate information with mapping technology
This allows Avalara to precisely determine nexus for a given address or location. You can see this in action with Avalara Sales Tax , a sales tax calculator with map-based geolocation. It's a free demonstration of the power and accuracy of Avatax.