Hello kjenkins,
It would be my pleasure to help you adjust the 401k deduction of your employee in QuickBooks Desktop.
We can correct the employee's year to date by creating a liability adjustment. If you still need to determine the amount on the payroll that needs to be adjusted, you can run the Payroll Summary report.
I'm linking an article below with the detailed steps on how to perform the process step by step including the liability adjustment:
Adjust payroll liabilities.
Please reach out to me here should you need any further assistance, I'm always available to talk QuickBooks.