If a peer-to-peer (P2P) loan is not repaid, then the loss that the lender suffers on that loan will be set against the income that they receive on other P2P loans before that income is taxed.
Legislation is proposed for the Finance Bill 2016 but relief is likely to be available for the current tax year.
It is proposed that P2P lenders who suffer bad debts on P2P loans that meet the conditions for relief between 6 April 2015 and 5 April 2016 will be able to claim relief in their tax returns.
For full details, see the HMRC proposed technical criteria document