I need to use five digit zip codes with SalesTaxII.
The use of 5 digit zip codes is allowed, but accuracy may be noticably reduced.
Using Signature Code or City Name with Zip+4 are the most accurate methods when accessing tax rates in SalesTaxII.
Please be aware that a 5 digit zip can be shared by more than one city and/or county.
To improve accuracy when using 5 digit zips, you should supply the city name along with the zip code. Even with city name misspellings, accuracy will be greatly improved.