I believe this is one that you are going to have to work with to ensure that the taxes are correct. So, in addition to the Tax Rule, the appropriate Tax Profile will have to be setup and used. Tax Rule -800023 is a regular wages rule, in that it will allow withholdings from all taxing entities. The way to control that is with the Tax Profile, by unchecking the appropriate boxes. Your customer should be aware of which tax(es) they are responsible for paying/filing for third-party sick pay.
You are welcome to contact me privately and I'll happily help with that setup!
------------------------------
Michelle Taylor
ERP Consulting Manager, CS3 Technology
918-388-9772
------------------------------