Three in five 16 to 54-year-olds have admitted to Canada Life their 'pension will' is out of date.
Just over 60 per cent of the 1,039 UK adults with private pensions surveyed by Canada Life said their nominated beneficiary or expression of wish form either required updating or they were unaware of its position.
Just 39 per cent confirmed everything was up-to-date.
An expression of wish or nomination form allows members of a pension scheme to document their preferences for their pension after death.
They are not legally binding, but scheme administrators and trustees do use them to speed up the distribution of funds to nominated beneficiaries.
Members will have been asked to complete the form at the outset of a pension being started by either the pension company, sponsoring employer to drawdown provider and should be regularly reviewed.
Without a current expression of wish form, payments to beneficiaries can be delayed or wrongfully paid.
Andrew Tully, technical director at Canada Life, said: "An expression of wish form is a vital piece of the pension jigsaw. Anyone who has a pension would have been asked at outset to complete a form to nominate who should receive the benefits of the pension in the event of their death.
"Given the complexities of life and how things can change so quickly, it is hardly surprising many people said their form is out of date. But that shouldn't excuse the fact these forms are vital to help pension trustees and scheme administrators pay benefits not only quickly and efficiently, but to the right people.
"Think of them as a 'will for your pension' and ensure you keep it up to date if your personal circumstances change.
"This approach continues into retirement if you have decided to use drawdown to manage your finances, as again, any pension funds beneficiaries stand to receive will be paid more quickly and to the right people if the form is current. In addition, as the legislation is more complex than it needs to be, nominating people is likely to allow more flexibility for benefits to be passed on in a tax efficient way."
Jessica List, pension technical manager at Curtis Banks, said: "Even though scheme administrators can exercise their discretion to choose beneficiaries, under the current rules an expression of wishes could also still affect the options available to the beneficiary and, ultimately, the amount of tax they may pay.
"The importance of having an expression of wishes and keeping it up to date cannot be understated."
Jenny Turton is a freelance journalist