The government no longer provides a specific social security benefit to help homeowners in receipt of certain benefits to cover the interest payments on their mortgage.
As of 6 April 2018 this was replaced by the offer of a secured loan to help cover capped levels of interest on mortgages for those who have been in receipt of a qualifying benefit (please refer to the below link for full details) for a continuous period of 9 months/39 weeks. Those in receipt of Pension Credit can access this support immediately.
As well as being secured against your property, interest is also charged against the sum loaned. You can make voluntary repayments to clear the sums borrowed from the Department for Work & Pensions, but they will not insist on repayment until the house is sold or title is transferred.
You do not have to claim this but if you feel this would best assist you in meeting your ongoing housing costs then it is something you can consider. You should seek specific advice on the effects of creating an additional security against your property.
If you turn down the offer at first, you can still accept it at any time as long as you’re eligible for SMI. The payments to your lender will be backdated to when you were first entitled to the loan.