How do I void a paycheck that the taxes have already been processed for?

Let me help you void the paycheck in QuickBooks Online (QBO), konjoian.

When voiding the paycheck, this changes your paycheck records and updates the dollar amount to zero. You may need to make adjustments to balance your books and this does not stop a direct deposit from processing and the funds doesn't return to you. Here's how to void it:

1. Go to Payroll menu.
2. Select Employees.
3. Choose Paycheck list.
4. Select the paycheck(s) you'd like to delete or void, then tap Delete or Void.
5. Press Yes to confirm. 

To learn more about this one, see the Delete or void employee paychecks article. If you are unable to delete or void, you'll see a message explaining why it happens. In this case, we recommend to contact our Payroll Support Team to void the paycheck. You may call us at a time convenient to you, send a message via chat, or we’ll get in touch with you instead. To ensure we address your concern, our representatives are available from 6:00 AM to 6:00 PM on weekdays and 6:00 AM - 3:00 PM on Saturdays, PST. See our support hours and types for more details about this one. Here's how:

1. Go to the Help icon on the top right. 
2. Enter your concern in the search field.
3. Choose Talk to a human.
4. Click the OK. To get you to the right human, in a few words, tell me what you need help with option and tap I still need a human. 
5. Press Contact us.
6. Tick Continue. 
7. Choose Chat or Get a callback.

Feel free to visit our Payroll page for more insight about managing your payroll transactions in QuickBooks. 

Please update us on the result after trying the steps or after contacting our support agent in the comment below. I'd like to ensure this is resolved for you. You have a good one.