Martin Lewis has issued a two-week warning for almost one million people to become eligible for the £301 cost of living payment.
The call to action from the MoneySavingExpert.com founder is focused on Pension Credit.
Pension Credit is available to people who have reached state pension age and are on a low income - but many households are missing out on this benefit.
If you’re eligible, Pension Credit will top up your income to £201.05 per week for single people and to £306.85 for couples.
Those who are entitled to the extra help could be on average £3,500 a year better off, according to the Department for Work and Pensions.
Pension Credit claimants are also entitled to the £301 cost of living payment, which started to be sent out to households last week.
You can backdate Pension Credit by three months and the deadline to do this, and be entitled to the £301 cost of living payment, is May 19.
Writing in the latest MSE newsletter, Martin said: “There is a deadline for the nearly one million pensioner households MISSING OUT on vital help they're entitled to.
“You've only until May 19 - two weeks away - to sign up for pension credit that'll trigger eligibility for the current £301 cost of living payment.”
Pension Credit - what you need to know
You might be able to claim Pension Credit if you are over the state pension age, and you live in England, Scotland or Wales.
The state pension age is currently 66 for both men and women, but is rising to 67 by 2028.
Pension Credit comes in two parts. You may be entitled to one or both elements, depending on your circumstances.
The Guarantee Credit element of Pension Credit tops up your weekly income to:
£201.05 if you’re single
£306.85 if you have a partner
Your income needs to be below these amounts to claim Guarantee Credit.
In some cases, you might still be eligible if you have a higher income and you have a severe disability, you're a carer or you have to pay housing costs, such as a mortgage.
If you reached State Pension age before April 6, 2016, or you have savings or a second pension, you may be eligible for the Savings Credit element of Pension Credit.
You could get up to:
£15.94 if you're single
£17.84 if you're a couple
You might get additional payments if you’re a carer, severely disabled, or responsible for a child or young person.
As an example, you can get an extra £76.40 a week if you have a severe disability, or an extra £42.75 a week if you look after another adult.
If you’re responsible for children or young people, you could get an extra £61.88 a week for each person in your care.
This increases to £72.31 a week for the first child if they were born before April 6, 2017.
If the child or young person is disabled, you could also get an extra amount of £33.67 to £104.86 a week if they get certain benefits.
Pension Credit also unlocks other perks, such as free TV licences for over-75s and help with housing costs, council tax and heating bills.
You can apply for Pension Credit online on the Gov.uk website, by calling 0800 99 1234, or by printing out and filling in a paper application form.
