If you bought a with-profits bond at the turn of the millennium, there are 364 days this year where you could face a penalty of up to 20% if you cash it in - £2,000 on a £10,000 policy.
But an estimated hundreds of thousands of customers won't face a penalty if they cash it in on the exact date of the 10 year anniversary of the policy.
Many people who bought a with-profits bond 10 years ago are being urged to dig out their paper work and check the exact date.
Strategy director of Skandia financial services, Michelle Cracknell, explains the details.
This item was first broadcast on Radio 4's Money Box on Saturday, 30 January 2010