If you missed entering the basic rate for new joiners, you may follow the steps below to enter the basic rate:
Go to Payroll, Modules and select Basic Rate Progression.
Search for the employee, enter the New Basic Rate and click Save
Go to the Payroll module, Pay Record.
Click New and click Next.
Select the employee and click Confirm.
After initialising, you may see the pay record in the pay summary for this new joiner.