Pretax Deductions

In most payroll programs by Intuit you would set up the Ins Pre-Tax item properly and in the next check add back to the check the incorrectly setup item with the amount deducted  last payroll as an addition, not deduction and then deduct the amount using the correctly set up payroll item for both weeks.  That should zero out the wrong item, have 2 weeks worth in the correct item and taxes will reflect properly. 

If IOP does not allow adds in deductions, you can void the original check in the books and reissue the same check with your correctly set up payroll item with the different in net pay put to "advance" or "Advance repay" and then add that deducted amount (the error in taxes) to their next check.

After you have run the payroll make the incorrectly setup payroll item as inactive so you won't accidentally use it - you can also rename it to prevent misuse (name it Do Not Use, or XXIns.)

How do you do it as an addition instead of a deduction?

Thanks for getting back to us, @CRJames70.

You can create a reimbursement to pay back the employee of the amount that was incorrectly taxed. I'd be glad to walk you through the steps.

1. Click the Employees tab.
2. Select the employee's name.
3. In the Pay section, click Edit.
4. Under What additional ways do you pay employee, select Show all pay types.
5. Check the box beside Reimbursement.
6. Enter the amount.
7. Hit OK.

Once completed, I'm confident that the amount that was incorrectly taxed will be given back to your employee.

Here's an article for your reference: Create a Reimbursement Pay Type in Online Payroll.

On the other hand, you might also want to read this article to learn more setting up deductions: Add, Edit, and Delete a Payroll Deduction Item.

Let me know in the comment section below if you have any other questions.  It'll be always my pleasure to lend a hand.