Overpaid an employee - can I claim back the NI or tax that the employee would have also over paid?

Hello there, BeanFrog. 

May I ask what kind of subscription you have? If you're using Advance payroll, I can guide you on how to back-calculate your national insurance contributions in QuickBooks Online.

Here's how:

1. Go to Payroll, and select the Pay runs tab.
2. Select the current pay run.
3. Select the > arrow next to the employee's name.
4. Select Actions.
5. Select Back Calculate NI.
6. Select the category used for re-calculation.
7. Enter the relevant from and to dates–this must be in the same tax year.
8. Select Calculate. A breakdown of what the original NI contributions were and the new NI contributions will show.
9. Once you are happy with the figures, select Apply.

Moreover, if you utilize a Standard payroll, I suggest reaching out to our customer support team. They possess the essential resources to assist you in examining and addressing this type of issue. Here's the process:

1. Log in to your QuickBooks Online company.
2. Select Help (?).
3. Proceed to the Search tab and select Contact Us.
4. Choose the topic you need help with or tap on Ask about something else, then type in your concern.
5. Click on Continue.
6. Pick how you would like to connect with our support.

For future reference, here's an article that will guide you in preparing your tax forms and wrapping up this year's payroll: Year-end checklist for QuickBooks Online Payroll.

If you have other concerns regarding the national insurance, don't hesitate to post here in the Community. We are eager to help you.