Around 70000 people mainly women have two months left to boost their basic State Pension and get backdated payments.
People who have reached, or will reach, State Pension age between April 2008 and April 2011 and don't get a full basic State Pension, could increase their payment and get it backdated, if they buy back National Insurance contributions in the next two months.
The special offer allows this group to buy back up to six years of voluntary contributions as far back as 1975.
Pensions Minister, Steve Webb said:
"We know that many women didn't benefit from the reduction in the number of qualifying years of National Insurance contributions needed to get a full basic State Pension and many have gaps to fill.
"Thousands of people could benefit from receiving back payments on top of a pension boost for life that could cover the up front costs of buying contributions.
"The chance to take advantage of this offer will end on 5 April of this year, so it's important that people act quickly."
People will still be able to fill gaps in their National Insurance records when this offer expires but the voluntary contributions won't be backdated.
In April 2010 the number of qualifying years of National Insurance contributions needed to get the full basic State Pension was reduced from 39 to 30 years for women.
Legislation introduced in the 2008 Pensions Act allows certain individuals to buy up to an additional six years of voluntary Class 3 contributions for tax years from 1975/76. To be eligible:
Individuals must reach State Pension age between 6 April 2008 and 5 April 2015; and already have at least 20 qualifying years, which can include full years of Home Responsibilities Protection.
The additional years can be purchased over and above those that can be bought under the usual time limits, normally the previous six tax years.
Those over State Pension age who pay under this offer by 5 April 2011 can have the voluntary contributions backdated to their State Pension age and may be eligible for arrears.
A full year of voluntary Class 3 National Insurance contributions currently costs around £625.
Further information can be found in "When and how to top up your National Insurance contributions" on Directgov www.direct.gov.uk or call 0845 604 2931. Here is an example of how it could work:
Anne - born May 1948, turned 60 in May 2008
Married, with 3 children. Worked part-time on and off throughout her working life.
She currently has a reduced basic State Pension of £82.03 a week compared to the full basic State Pension of £97.65.
If she paid just over £2,500 for 4 years of additional voluntary contributions her basic State Pension would go up to the full rate for the rest of her life. At current rates that's an extra £15.62 a week.
And if she paid the additional voluntary contributions by 5 April 2011 she would also get arrears - backdated to when she reached her State Pension age, in May 2008 - amounting to over £2,000.