If during the year 01 April 2019 to 31 March 2020 you began receiving payment your previously deferred pension from Staffordshire Pension Fund, you will have received a Pension Increase to your annual pension which was shown on your April 2020 payslip.
The additional payment labelled as “Grant PI”, if shown on your November 2020 payslip, represents the Pensions Increase from 09 April 2019 to your date of retirement which is due on the Lump Sum which you have already received.
For example, if your pension started to be paid on 01 October 2019 you are entitled to Pensions Increase on the lump sum for the period 09 April 2019 to 30 September 2019. The part increase for the year would be 0.85% compared to the full 1.7% increase for the whole of 2020.
This “Grant PI” increase is a one time only payment, made in the year following the commencement of your pension.