Deductions are applied differently than allowances.
Within payroll if a deduction is added, this sets a flag that there are monies to be deducted from the employee's pay.
If the deduction is applied within a pay run where there is not enough Gross or Net to cover the amount, this will lay dormant until the employee has enough pay to cover.
Currently there are no warning messages for these events
To confirm why the deduction was not applied, review the employee's pay record for the affected period and confirm if the Taxable gross or Net was enough to cover the deduction.
Example: Joe has a $100.00 post tax deduction applied for the month of May. Joe has the entire month of May off as unpaid leave unexpectedly. As there is no available Net the deduction was not made. June, Joe is paid as normal and the $100.00 is deducted from his net pay.
Correcting a deduction applied in error
If the deduction was processed in error, this can not be deleted as the transaction has been processed. To correct, you will need to apply a deduction of the same amount but with a negative value.