In our Time Evaluation Schema, we have function IF with Par3 = EOP, followed by one or more PCRs, either called by function ACTIO (to generate special WTs) or called by function P2006 (to generate Quota Balance WTs). These WTs are transfered to Payroll through table ZL, and are generated only on the last day of the Payroll Period.
It would be easy to create a Payroll PCR to look if a certain WT (created on EOP day) exists in the IT (after importing ZL) and generate an error if it doesn't.