I can share some information that can help you with processing a terminated employee, @RG_0303
You'll just have to run the final payroll and then, send an FPS to inform HMRC about the termination. In QuickBooks Online Payroll Standard, mark an employee as a leaver from the Payroll menu. Once done, create a P45 to close the employment record from the Documents on the individual employee's profile page. For detailed guidance on how to do this, check out this article: P45 form in QuickBooks Online Standard Payroll.
If you're subscribed to QuickBooks Online Payroll Advanced, refer to the following articles on terminating an employee, processing a termination payment, and issuing a P45 form:
For more information on what you can do after terminating an employee, refer to this link for more information: What to do when an employee leaves.
Check out these articles for step-by-step instructions for specific features in managing your employees' QuickBooks Online Advanced Payroll and Standard Payroll:
Let me know in the Reply section if you need further help with processing a terminated employee. Keep safe, and have a wonderful day!