Knowing what tax codes to choose for your transactions is an important part of managing your business. When it comes to QuickBooks Online, the built-in payroll module is great so you don't have to worry about recording it as an expense. Here's an article about the program's Standard and Advanced Payroll features.
If you're looking to record payroll outside of the payroll module, here's a look at how you can do that in QuickBooks Online: Record payroll transactions manually
If you're looking to record an employee reimbursement, here's a helpful link on how to do that.