CPP and EI on Retro Payment

I retired from the PS as of mid January and received my last regular paycheque this past Wednesday - after a 16 month delay, I received retroactive pay on the last cheque covering the difference between my substantive level and the acting level up to the time of my retirement. I had been regularly hounding our HR team for over a year to process my retroactive payment.

The kicker is that almost $2200 in CPP and EI was collected out of my retroactive pay even though I max out my EI and CPP contributions halfway through each tax year. So if the retro payment was processed last tax year I would not have been dinged $2200.

Does anyone know of any options to seek an exception for this deduction or some type of possible credit that could be applied for the 2025 tax year?