Hello there, AcctnAsst.

Allow me to step in and provide some additional information on how to handle and resolve the payroll error you experience in QuickBooks Desktop.

You have two options to correct this. You can either manually calculate the gross wages or create a new Salary Item intended for the underpaid employee. Since you can only use a Salary Item when you select the Enter net/Calculate gross option, you may need to create a new Salary Item as an alternative. 

To create a new Salary Item, you can follow the steps below:

1. Go to the Lists menu.
2. Choose Payroll Item List.
3. From the Payroll Item drop-down, choose New.
4. Select Custom Setup. Then Next.
5. Select Wage. Then  Next.
6. Select Annual Salary. Then Next.
7. Select the type of pay. Vacation Pay and Sick Pay are each specific options. All other types of pay should be entered as Regular Pay.
8. Select Next and follow the onscreen instructions.
9. Click Finish.

Once done, you can start creating payroll for the underpaid employee and use the newly created Salary Item, then enter the amount you paid for the employee.

I'm adding this article as your reference on how to set up a Salary payroll item: Set up a yearly salary payroll item.

If you choose manually calculate the gross wages in QuickBooks Desktop, here's an article that provides a detailed: Calculate gross wages.

That's it. You should be all set. Never hesitate to get back to me if you need further assistance while working with this. It's always my pleasure to help.