You've reached the right place for help. I'd be happy to answer your question. I want to make sure I'm understanding you correctly, you're looking to deduct $100 on your employees cheque?
Before we get started, I'd like to ask a few details so I can give the right setup for this.
The calculation of taxes in QuickBooks Online Payroll is based on the TD1 information. May I know what particular tax is this $100 deduction for? You can be as detailed as possible, so we can have the right setup for your employee.
It's nice to see you joining us here. I would be glad to provide the information needed, to make changes to the requested amount to be withheld from your employees paycheque, in QuickBooks Desktop.
Although QuickBooks updates the information provided by the CRA, to calculate the amounts on the TD1, you can also manually change the amount, when requested by your employee(s). Here's how;
1. Open the Employee tab and select the employee you need to update
2. Select the Edit icon beside employee information