Working Brits could miss be missing out on thousands and thousands of pounds by being overly optimistic about when they plan to retire.
That's because your pensions savings are designed to grow fast early on, but take fewer risks as you approach retirement.
This stops a late crash in the markets hitting your savings when you don't have the time left to rebuild it.
But it also means as you approach the date you've set to retire, growth slows right down.
And that means people who are overly optimistic about when they will cash in their retirement savings could be missing out on a lot of years of growth.
Colin Williams, managing director of workplace savings and retirement at Aviva, said: "De-risking profiles have been carefully designed to balance risk and return in the approach to retirement.
"But this balance is thrown out of kilter if someone wants to retire at a different age than was originally assumed when they started their pension."
Aviva worked out that an average earner in their company's automatic enrolment pension could miss more than £4,000 in their pension pot by using a default retirement age of 65, but then actually retire at 68 - the current state pension age for under-40s.
By contrast, if they put their age at 60 - the old state pension age for women - they would miss out on almost £9,900 if they worked on to the current one.
The good news is it's easy to check and fix.
“Changing your retirement age is a really simple way to maximise the potential returns of your pension investments," Williams said.
“Many providers allow you to check and change your retirement age online. I’d encourage people to go online and check the retirement age their provider holds, and if doesn’t match their current plans, change it.”
As to what age you should pick, it's simplest to choose the state pension age - unless you're confident you'll have enough to quit work early and live on your savings alone for a few years.
If you're not sure what your state pension age is, you can check it here .
