More than 6 million people have not banked enough contributions over their working lives to qualify for the full state pension.
Current rules require at least 30 years of contributions for someone to receive the full state pension, but from April 2016, this rises to 35 years.
However, the average person reckons they will have a full-time job for 37 years – but 28% have only clocked up 28 years.
Most of those who fail to hit the threshold are woman who took time off to raise a family, says financial firm Partnership, which carried out the study.
The average for women with insufficient working years rises to nearly 40%, while for men, the average is nearer 14%.
Women bear the brunt
The numbers also vary regionally, with 35% of workers in Wales failing to tick off the full number of qualifying years, while the number drops to 19% in London.
Researchers spoke to more than 1,000 40 to 70 year olds to find out how many will be paid a full state pension.
Besides taking time to look after a family, the other most common reasons for falling short in qualifying years are medical problems (28%) or unemployment (27%).
Some returned to full time education (11%) and one in 10 did not work as they cared for a friend or relative.
Pension rules credit state pension qualifying years to the unemployed, anyone receiving benefits for a child under 12 or who act as full time carers – providing they claim for the allowances, which many people do not, says the firm.
Pension planning
Anyone with a lack of qualifying years for a full state pension can top up their national insurance with voluntary contributions, but in many cases the cost is not worth the return in pension benefits.
Partnership’s Andrew Megson said: “People planning their pension income assume they will receive the full state pension, but this is not necessarily the case, especially for women.
“This can mean a nasty shock on retirement if people have not checked out what their state pension entitlement may be.
“Our research shows around three out of every 10 people are in this situation and we believe everyone should ask for a pension report to see how much money they are likely to get.”
Finding out what the state pension payment is likely to be early on gives people time to save to make up the shortfall, explained Megson.
