Get our money-saving tips and top offers direct to your inbox with the Mirror Money newsletter Sign up Thank you for subscribing We have more newsletters Show me See our privacy notice Invalid Email

Failing to make a claim - or following up once you have - could leave you tens of thousands of pounds worse off.

Moreover, the DWP doesn't even know how many eligible people are missing out or what it owes them, according to a Freedom of Information request from Responsible Life .

The firm asked the question after one of its customers - Peter Williams - was handed an astonishing £132,800 worth of back payments for his state pension.

He had filled out the forms to start claiming his state pension 11 years ago, but when he heard nothing back he assumed he wasn't eligible for the £168.50 a week payout - so found a way to make do without it.

It wasn't until he reached the last £200 in his account, when he decided to take some equity out of his home to help cover some improvements, he found out about the missing cash.

Video Loading Video Unavailable Click to play Tap to play The video will start in 8 Cancel Play now

The equity release firm conducted a review of his finances - which is when they discovered the astonishing amount he was owed - along with the extra money he was due each week.

"Words cannot describe the elation I feel," Peter said after finding out.

Responsible Life managing director Steve Wilkie said: “Any number of people who have reached state pension age could be missing out on millions of pounds.

"It sickens me to think of the sacrifices some will be enduring to make ends meet, unaware that those hardships are completely unnecessary."

(Image: Peter Williams)

The DWP said it did not hold data on people who haven't started claiming their pension, or how much they could be owed.

It also doesn't remind people.

“Invitations are issued to prospective SP (state pension) customers 4 months before state pension age," the DWP said.

"There is no legal requirement for DWP to notify people, either individually or generally, about eligibility for state pension; however, DWP provides a claim invitation to ensure as many citizens are prompted to claim. Reminders are not issued.”

Wilkie is now urging anyone over 65 not receiving the payment to check now to see if they're owed cash.

“We will never know much money is collecting in the government’s coffers instead of being returned to people who have contributed all their lives but it’s time the government did the right thing," he said.

“We have seen first hand how windfalls are waiting for those who have not claimed their state pension for a variety of reasons.

“Reminding people that they are entitled to a state pension is the responsible and the right thing to do.”

Steve Webb, director of policy at insurer Royal London, said: "If you are over pension age and have not received anything, you should call the Pension Service.

"If it does not hear back, the Pension Service assumes that taxpayers want to defer their state pension. But the letter may not have reached its destination."

A Department of Work and Pensions spokesman said: "We want everyone to be able to claim what they are entitled to and have a wide range of channels where people can get information and advice."

You can claim online at gov.uk/get-state-pension or find out more about the state pension, here.