Pensioners are being urged by the Government to check whether they are missing out on a potential boost to their retirement income.
As many as four in 10 pensioners could be missing out on pension credit - with more than £3.3 billion going unclaimed - an average annual amount of £2,000 for each entitled family who do not claim.
Government figures show that nearly two million pensioners are boosting their retirement income and benefiting from the additional support of pension credit.
In 2015/16, more than £6 billion in pension credit was claimed by people on low incomes to help cover their basic costs of living.
Guy Opperman, minister for pensions and financial inclusion, said: "With billions unclaimed, I urge everyone to check that they and their relatives, friends and neighbours are claiming the pension credit they are entitled to.
"Through a simple check, you could have access to additional money that could make all the difference in day-to-day life."
Pension credit is a non-taxable benefit based on a person's income, providing pensioners with a minimum level of weekly income if below £159.35 for single people or £243.25 for couples.
Additional amounts may be payable for people with caring responsibilities, severe disabilities or certain housing costs.
:: For more information on pension credit, visit www.gov.uk/pension-credit, where a calculator can establish whether you may be eligible and how much you could receive.