Hi there, amcLLC.
QBO Payroll supports both pre-tax and taxable employee deductions. A taxable deduction might have selected when the deduction was set up.
Make sure to select the correct payroll item and type so it'll be saved as a pre-tax deduction (see attached screenshot).
More information about the different payroll types and deductions that are supported in QBO are discussed here:
I'll be around if you need anything else.