If this is regarding claiming EI premium overpayments on Box18 on your T4 slips for prior tax returns, you are allowed to claim the amount up to the last three years only. EI premium overpayments claims can go back 3 years and CPP contribution overpayments claims can go back 4 years.
On the TurboTax Desktop/Download, you will need to override the overpayments from the schedules 8 and T2204 > when you try to override the payment it will deny it > click ok on the pop-up window > click F2 > accept the condition in the new window > change the amount to zero
For your reference:
EI premium rates by year:
CPP contribution rates by year:
If you still have issues after following this process, please contact our support line: https://support.turbotax.intuit.ca/contact/
I hope this was helpful
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