The average age at which people write their will is 47, a survey has found.
But six in 10 (61%) people surveyed by Which? Legal say they have no will in place, with 38% of these people claiming to have nothing worth inheriting.
A fifth (20%) of people with no will in place say making a will had not occurred to them, while 16% claim to have been too busy.
Which? Legal found that those who did have a will in place waited until they were 47, on average, before writing it.
The survey found fewer than a third (31%) of people in Scotland have written a will, compared with 35% in Wales.
In England just over two-fifths (42%) of those surveyed have a will in place.
Nearly half (47%) of people surveyed in Northern Ireland have a will.
The research also found 57% of 18 to 24-year-olds say they would leave money to charity in their will, while 19% of those aged over 65 said they would make some form of donation.
Darren Stott, managing director of Which? Legal, said: "It's clear that people don't appreciate the risks of not having a valid will in place.
"Even if you think you have nothing worth inheriting, this is often not the case.
"Whatever stage of life you're at, a will offers peace of mind and ensures that your money, property and other possessions go to the right place.
"Giving money to charity in your will can be a tax efficient way to pass your money on."
More than 2,070 people across the UK were surveyed.
Here are the percentages of people with a will, according to Which? Legal:
- South West, 47%
- Northern Ireland, 47%
- Eastern England, 44%
- East Midlands, 44%
- South East, 40%
- North East, 36%
- North West, 36%
- Wales, 35%
- West Midlands, 35%
- Yorkshire and Humberside, 34%
- Scotland, 31%
- London, 31%