Let's find out the reason why your paychecks have stop calculating taxes.
Employee W-4 information (wage amount, marital status, pay frequency, and allowance) is one of the criteria to consider why QuickBooks has stop deducting taxes. Let's make sure that you've entered the employees's W-4 correctly.
If the employee's information are correct, let's go some troubleshooting to fix this payroll issue.
For QuickBooks Desktop payroll, you can run the latest tax payroll table. Delete the paychecks and create the them again. If you're still getting the same result, go ahead and revert the employee's paycheck. On your Enter Payroll Information screen, right-click on your mouse the name highlighted in yellow then choose Revert Paycheck. It helps to refresh the system and recalculate the taxes.
For QuickBooks Online Payroll, please delete and recreate the paychecks.
If you have any questions, please let us know. Thanks!