There are two important issues specifically related to payroll with Sage100.
If you are not on Version 2018 or later of Sage 100 you should make that upgrade sooner than later. There are updates specifically related to exemptions and the new W4 that are part of the latest upgrade of Payroll 2.20 which is only compatible with Version 2018 and Version 2019 of Sage 100.
The second is if you ARE on Sage 100 Version 2018 or Version 2019 and not on the payroll version that was released in December of 2019 there is a bug that will cause excessive withholdings tax to be calculated if your payroll check is dated 12/31/2019 OR 01/01.2020.