Like many other aspects of PeopleSoft, effective dates play a key role in administering employee benefits.  Whenever a manual event is added to the BAS Activity Table, be sure that the event date is correct.  By default, the system assigns whatever the current date is as the event date, so it is likely that you will have to adjust that date.  Be aware that the date will determine not only the enrollment or termination dates for that employee's benefits, but also when the deduction begins or ends.