Question Regarding ESA and Incorrect NI Contribution Adviced Needed

Hi all,

I feel I am currently stuck in a very complicated situation here.

I got really ill last winter, stopped working, and applied for New Style ESA. I was told that because I did not pay enough NI, I would only get credits. So I checked my pay slip and realised there was a mistake: an overpayment (which I later paid back) was added to my relevant years instead of the overpaid years. As a result, my NI contribution was reduced and not full.

So I got in touch with payroll, who said they made changes at the end of last year. Then my NI contribution page changed to some very large number, so I thought something was not right, but I thought maybe it would be corrected as we approach the end of the tax year.

I called HMRC today, and they can't see what my employer updated, but think there were mistakes in the update. So I got in touch with payroll again today.

Meanwhile, the whole ESA and WCA pushed on, and I had my WCA just this week.

Now the question is, what can I do after I receive my WCA decision, let's say 2 months later, my HMRC finally gets corrected, and I am due payment instead of credit? My earlier understanding was I needed to submit MR if I want to change from credit only to payment, but now HR is going to be super slow so I don't really know what is going to be my grounds for MR, and how to carry this forward!

Advice is much needed! Thank you!