...
A certifiable PSPA will reduce a member’s RRSP contribution room for the current year (i.e., when it is processed by the CRA). The amount a member pays for past-service benefits will not likely equal the PSPA associated with the benefits because the PSPA measures the value of the past-service benefits, rather than how much it costs to pay for the benefits. A PSPA may also be triggered when the Plan benefit is improved for past service, as occurred for the benefit improvement effective January 1, 2018 and , April 1, 2021 and January 1, 2023, for service prior to those dates. This type of non-certifiable, or exempt, PSPA does not require CRA approval and reduces RRSP room in the year after the PSPA event occurs.
...