I cant make a t4 for a former employee

Hi there, 

Welcome to QuickBooks Community. The program is designed to help you streamline your work using the powerful features in the program. 

The reason why you're unable to produce a T4 is that the employee is inactive. I recommend reactivating the employee using the steps in the following article that shows you how to: Make an inactive employee active in QuickBooks Online Payroll. After doing this, you can follow the following article that shows you how to: Prepare and submit T4 slips and T4 Summary in QuickBooks Online. 

Let me know if this info helps. I'll be a message away in case you have other questions.