For companies with a limited range, my clients typically just hand enter them.

If they have a larger range, they go to something like Avatax and it becomes totally automated.

Note that use of zip code is not entirely accurate way of determining sales tax jurisdiction.  It can be close but isn't perfect.

Hi Tom,

Thanks for answering, but when you hand type them it still go by zip code is that correct? In order to have all zip codes and tax rates and all cities of a state, we might need to do a import, but some city names are longer than what sage 100 field allowed . What fields and what table we need to update inside of Sage 100. Just wonder what smaller companies are doing if they cannot afford Avatax

Sorry for a slow response.  Didn't see this until now.

Out of the box Sage 100 would still go by zip code or by state. 

Updating rates would be in SY_SalesTaxCodeDetail.

Updating zip codes with tax schedules would be SY_SalesTaxScheduleZipXref.

Thanks Tom!