GOV.UK
Undisclosed Partners: Recovery of Overpayment for cases opened before 17 May 2007 - Previous Claims Made By Both Partners
Where both partners have previously made claims as single customers you will be looking at two incorrect claims and will have two separate enquiries. They will each be responsible for their gross overpayment but from each figure you can deduct their share of the notional entitlement.
You will need to calculate the amount they could have claimed as a couple and then allocate this between them. How you allocate this amount between the parties will depend on their wishes. If they specifically ask for it to be split in a particular way you should go along with their proposal as long as they are both in agreement to it. If they do not stipulate how this should be split or cannot agree the split you should divide the notional entitlement equally between them.
The net overpayment on each case will be the difference between their respective gross overpayment and their amount of notional entitlement. Their respective penalties will be based on their net overpayment.