CPWP/CPWPA Certification Renewal and On-going Professional Training (OPT)

Does the OPT requirement need to be met on an anniversary basis?

No, the OPT requirement only needs to be met on a calendar-year basis.  For avoidance of doubt, there is no OPT requirement for the year the CPWP/CPWPA certification was obtained.  The OPT requirement only starts in the succeeding calendar year.