When adding additions to basic pay you will only be able to select pay elements that have been set up as additions. Similarly, when adding deductions you will only choose between the elements set up as deductions.
This needs to be set up when the pay element is first created.
Click Setup, then Settings.
Click Module Settings and select Payroll Settings.
Click Pay Element, then Add Pay Element.
Set up the pay element as needed.
To determine whether this is a deduction or addition, select between the options below from the Type dropdown:
Cash Deduction
Cash Payment
Number of Units in Decimal
Number of Units in Decimal Deduction
⚠️ Important: Once the element has been set up and added to employees it is not recommended to change its type. In this case you will need to set up a new element rather than edit the existing one.