Does anyone know how to edit the bonus only tax amount?

Hello aidancabral26-gm, 

Welcome to Community!  It's great to hear that you're looking to provide your employee with a bonus cheque.  QuickBooks Online Payroll calculates the amounts based on the information entered in the employee profile, as well as the regulations provided by the CRA. When you need to adjust the tax amounts, you can do this prior to submitting payroll.

Please note that only an accountant or bookkeeper will have the ability to edit employee and employer tax amounts while running payroll, and some restrictions apply.  Follow this link to learn how to edit employee and employer payroll taxes in QuickBooks Online Accountant.

If you have any other questions, feel free to reach back out.  We would be glad to help!