Your pensionable service is a key part of the formula used to calculate your future MEPP pension. The more service you have when you retire, the larger your pension will be. You earn service for every day that you contribute to the Plan and, in certain cases, you are also permitted to buy previous service.
For example, if you are off from work for a period of time and not paid (Leaves of Absence) or are not contributing to the Plan, this will create a gap in your pensionable service. You can purchase this service to ensure there is no service gap.
We call purchasing service this way a buyback.