Pensioners are the least likely to have checked their pension benefit entitlements, meaning millions of pounds is left unclaimed each year.
According to research by national poverty charity Turn2us, 63 per cent of Britons who are of pensionable age have never checked to see what benefits they can claim.
They are also the least likely age group to claim any benefits to which they are entitled, which means one in three is missing out on what could be invaluable pension credit.
Sonya Ruparel, director of programmes and partnerships at Turn2us, said: "There is an endemic issue of unclaimed benefits in the UK.
"The confusing, sometimes hostile, and often stigmatising world of social security has led to millions of people not claiming their entitlements."
Turn2us collected government data and carried out internal estimates on benefit claims. It also commissioned Censuswide to carry out additional research during March this year, among 2,000 UK adults, to ascertain what level of understanding Britons had when it came to benefit entitlements.
The charity found that more than 7.1m people could be missing out on £15.1bn worth of benefits, with 45 per cent of the population never checking to see their eligibility for various benefits (see table, below).
It found that "institutional stigma, cultural shame and negative media representation of benefit claimants" were cited as some of the most common barriers preventing people investigating their entitlements.
Simon Gray, managing director of HUB Financial Solutions, said often pensioners and home owners do not realise they are entitled to claim any benefits.
He said: “Home ownership does not exclude people from claiming additional financial support, and it is important we get this message across to homeowners.
“Many retired homeowners do not have large incomes. These people could be missing out on benefits they are entitled to receive and that extra income would make a big difference.
"Benefits are made available by the government to help people in all sorts of situations, whether they are having to care for a relative, have an illness or disability themselves, or are entitled to a reduction in their council tax.”
People missing out
Income Support / ESA
Child Tax Credit
Working Tax Credit
Council Tax Support
In response to the findings, Turn2us has created a Benefits Calculator tool, designed in partnership with people who have lived expertise of claiming benefits.
The charity is urging people to check their entitlement and start the application process as soon as possible.
Ruparel added: "Our new tool sets out to simplify, de-mystify and compassionately support people to access the money they are due.
"It is so important for people to check. We urge everyone to do a benefit calculation every six months as part of a regular financial health check.”