MoneySavingExpert founder Martin Lewis urged anyone aged 45 to 70 to see if they can boost their state pension by up to £5,800.
But it's important to act quickly, as the big perk of the scheme ends in April 2023.
Speaking on The Martin Lewis Money Show on ITV, Lewis said: "If you're aged 45 to 70 you need to check ASAP if you can boost your state pension."
The top-up is open to people on the new state pension, brought in on April 6, 2016.
How much state pension you get depends on how many years you paid National Insurance (NI).
To get the full amount of £185.15 a week you need around 35 years of NI payments.
Some people are missing years of NI, so aren't eligible for the full new state pension.
This can be because they were abroad, or on low incomes.
Lewis urged people to go to gov.uk and check their state pension forecast, including their NI record.
This will tell you if you are missing any NI years.
"If you have a shortfall, you can buy more years," Lewis explained.
Until April 2023 you can buy NI years going back to April 2006.
But after April 2023 you can only buy NI going back six years.
"If you're near state pension age, it's easier to see if it's worth it for you," Lewis said.
"The younger you are the longer you'll have to plug any gaps."
Buying a year of NI costs around £800, and adds around £275 a year to your state pension.
"If you live three years beyond state pension age, you're quids in," Lewis explained.
"We're talking real money and it's really worth doing, though you will need to have the cash to do it."
Men aged 66 live for another 19 years on average, so each £800 spent could add an extra £5,300 to their state pension.
Women aged 66 typically live another 21 years, so each £800 NI year bought adds an additional £5,800.
But Lewis urged viewers to be careful and do their own research before committing.
"Don't rely solely on what you're hearing me say - always contact the Government Future Pensions Centre to work out what would happen in your case before you pay any money out," he said.
The full state pension is set to rise by over 10% next year after former Prime Minister Liz Truss claimed she will keep the triple lock.
Under the triple lock promise, the state pension will go up next April by the level of inflation in September.
Official figures out this month show that September inflation was 10.1%.
If the triple lock guarantee is kept in place, this means the full state pension will rise from £185.15 to £203.85 per week next year.
This marks an increase of £18.70 a week - or £972.40 over the year.
The basic state pension would increase from £141.85 per week to £156.20 per week under the triple lock - up £14.35 a week or £746.20 over the year.
