In some circumstances, you are required to issue more than 1 T4 slip for a single employee in a year.

If you have operations in both Ontario and Quebec, and a particular employee worked some of the year in your Ontario operation and some of the year in your Quebec operation, then you will have to divide up their earnings/CPP/EI/tax between the 2 provinces and prepare both an Ontario and a Quebec T4 for that employee. (This is true any time you have operations in more than one province - not just Ontario/Quebec). If this is the case, note that you will have to manually check that you have not gone over the CPP and EI maximums for that employee, as Simply does not 'understand' that "Employee A - Ontario" and "Employee A - Quebec" are the same person.

On the other hand, if your business only operates in one province, but you have an employee who moved during the year while still working for you, you only have to do one T4. Separate T4's are only required for separate province of EMPLOYMENT, regardless of where the employee chooses to live.