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All calculation for CPP contribution will be on Schedule 8 or RC381 form whichever applies, to calculate the amount, if any, of your overpayment to enter on line 44800 of your return. CPP contributions will show on line 30800 and overpayment on line 44800.
I discovered that the gross income from my T-$ slip did not transfer over to the CPP overpayment calculation page. Therefore it shows that with no income my CPP contributions were overpaid .This then carried to the refund page showing an over payment of CPP