I'd like to mark an employee as a leaver from a previous payroll period (Feb 2022) however as new payroll period has started, I am unable to enter a date from February.

Hello Moustafa1, 

welcome to the Community page, 

In order for us to help you with your questions, we need to know which exact payroll it is you use with us at Quickbooks, is it our Standard Payroll or our Advanced Payroll?