In the PIER Report all but one employee had overpayment for CPP.  That employee was the only employee that had a full 26 pay period.  The other employees were either hired later in the year, or fired during the year, so the payperiods were anywhere between 20 down to 12.  As they worked solid weeks, that shouldn't have affected the rates.  All personal tax credits, federal and provincial are correct, and payperiods per year is set to 26, for all employees.  Only 3 of the employees had Christmas bonus, as did the one employee who's CPP worked out correctly.  Vacation pay is not retained for any employee. 

What could be the cause of the overpayments in CPP