Just found this KB article; I didn't come across it initially:
Tax tables are not updated after installing Tax Table Update (TTU)
Products
Sage 100
Description
Tax tables are not updated after installing Tax Table Update (TTU)
Disclaimer
Backup Warning
Use caution when working with the below product functionality. Always create a backup of your data before proceeding with advanced solutions. If necessary, seek the assistance of a qualified Sage business partner, network administrator, or Sage customer support analyst.
Cause
Tax table is setup to be excluded from tax table updates.
Resolution
Go to Payroll, Setup, Tax Table Maintenance
Select appropriate tax table; FED or state
Uncheck Exclude the Table from Tax Update check box and reinstall Tax Table Update
Related resources
How to download and install the Tax Table Updates (TTU)
Category
Download and installation
Entitlement
Open
ID:57889Last modified:8-5-2016