Base salary changes shouldn't be done in advance as it can create wrong pay calculation for the ongoing payroll.
It is important to bear in mind that payroll must be processed before making any salary changes.
The current monthly payroll of company XYZ goes from 01/01/2022 to 31/01/2022. As today is January 15th, the January payroll hasn't been ran yet. Ellie gets a salary increase from 01/02/2022. If you were to record Ellie's pay rise today, January 15th, the salary increase would be taken into account starting from January instead of February.
Go to My employees
Select the employee by clicking on View
Scroll down to Regular pay
Make the desired adjustments and save