I appreciate you getting back to us, @justin61.
You'll just need to run your payroll when submitting FPS to HMRC. This way, QuickBooks will automatically calculate the payment that shows all employee payments and deductions. Let me guide you through the process.
I'm adding this article for more details: Submit FPS to HMRC in QuickBooks Online Standard Payroll (UK).
You might also want to check out this article to learn more about QuickBooks Online Standard Payroll.
Keep in touch if you need any more assistance with this, or there's something else I can do for you. I've got your back. Have a good day and stay safe.
Morning, thank you - I'm clear on all that.
Where I'm struggling is with the amendments that need to be done in this situation:
As we have an ex employee, who has already been marked as a leaver in his last pay period and issued with a P45, and who we now need to make an additional payment to (using a tax code 0T as specified by HMRC), we have had to set him up again as if he is a new employee to allow a payroll run. We will need to submit an FPS after payroll run as usual but with his original employee id entered and with the "payment after leaving" indicator set - both as specified by HMRC
It is the last two actions where we are struggling and need guidance.