Did you know that you can allocate payroll contributions and taxes to classes and jobs?
The first thing you need to do is make sure the Allocated payroll contributions and taxes preference is turned on.
To do this, go to Edit -> Preferences ->
Payroll & Employees -> Company Preferences
and check the box “Job Costing, Class and item tracking for Paycheck Expenses”
Once that preference is turned on, check the box “Track Expenses By Job” when you set up an item you’d like to allocate to jobs.
You can also go into “existing payroll item” and turn this feature on.
Quickbooks won’t go back and retroactively allocate prior transactions, but all future ones will be.