Issue reported in Dynamics AX 2012 R3.
Client reported that after installing 2018-R2 tax update that all workers earnings were negatively affected causing them to receive less per paycheck. The issue was submitted to Microsoft and (118013117566487) and tech stated that "There is a parameter called allowSupplementalElection, which determines whether or not the pretax 401k deduction should be applied to both regular and supplemental wages. We have this turned on by default in our code, which is causing the 401k deduction to hit both the regular and supplemental wages, driving down the taxable wages just enough to produce the 75 cent difference we are seeing. So the results that we see in the system are expected and by design.
In your example that you provided you do not want 401k deductions to be taken out of the supplemental wages, but we don't support that.
Since we have other customer who are using the system as it currently is and are expecting the results that we see the system calculate the way it currently is we cannot just switch the flag to false, either, as other customers are expecting the existing behavior.
I would recommend entering a product suggestion to have the system calculate"