People who give up work to care for relatives or friends are missing out on benefits worth nearly £750m, a campaigning charity says.
Carers UK says carers are missing out on millions
Carers UK said more than 300,000 over-60s are going without vital benefits to which they are entitled.
Nearly seven out of 10 older carers cannot afford adequate heating or clothing, it added.
The government said it recognised carers' contribution and wanted to make sure they got their financial support.
The report coincides with a national day of action to raise awareness of carers' benefits and rights.
Carers UK said because of the lack of awareness about benefit entitlement, many carers had to cut back on essentials.
There is evidence one in 10 older carers has to cut back on food to make ends meet, it said.
On top of that, carers are particularly affected financially in later life because when they give up work to look after someone they stop paying into a pension.
The report said between 40% and 60% of disability benefits went unclaimed.
The organisation said some carers missed out on Pension Credit entitlement and Carer Addition benefits, as well as discounts on council tax.
Carers UK chief executive Imelda Redmond said many older carers simply did not know what benefits they were entitled to.
"They often don't recognise themselves as carers, they wouldn't recognise the term, they wouldn't identify that with themselves and so they don't then necessarily go and ask for that help," she told BBC News.
"For every single benefit, the rules are very complicated.
"What I'd say to people is, if you are looking after someone who is sick or disabled and is dependent on you then seek some advice and some help and ask to see whether you are entitled."
Some older carers would rather go without benefits than endure the "intrusive questioning" of means testing, she added.
A Department for Work and Pensions spokeswoman said the government recognised carers' "valuable contribution" and it worked closely with organisations like Carers UK.
"We want to ensure carers know about and receive the financial support they are entitled to and get recognition in retirement for their role," she said.
"Carers can get additional money on top of their standard benefits and can build up pension entitlement when they are caring.
"Ministers have agreed that the pension system should produce fair outcomes for women and carers and we are currently consulting on these issues as part of the National Pensions Debate."
As part of its Carers' Rights Day, Carers UK is launching a new guide to benefits and services for carers over the age of 60.