I've been over-issued with pay 3 times over the last few months. Despite highlighting this to JPAC and HR, no action has been taken to recover it. So, it's currently tucked away in an ISA earning interest until they take it back. There seems to be no way to repay the money with a cheque as under the old system. If they're so determined to make me keep more money than I'm owed, so be it!