i received this warning at the end of tax session. I have tried to rectify and or find the problem, and can't seem too.
You have CPP contributions on self-employment and other earnings with CPP contributions on employment income. The result of the CPP contributions payable on self-employment and other earnings of Schedule 8 is negative. You may have an overpayment. In this situation, the CRA does not want an amount on line 448 and wants to calculate it for you.