There were no outgoing NI payments to offset against the SMP, so these had to be reclaimed from the Tax Authorities at the end of the tax year.

I posted the correct amount of SMP through payroll many years ago but HMRC overpaid by £14 and a few cents.

I am not sure what happened, the SMP went over two tax years. The first round of payments was just right. But the second payment was higher than what was reported by the payroll software.

Don’t know what to do. Was it an accidental overpayment or did they pay interest on it.

I really don’t want to go through the archives to find the cause of this overpayment. It’s not worth the time. If they are paying interest. I would rather write off the overpayment and credit it as interest received – if I know HMRC are paying interest.