About 50,000 Aviva customers will be refunded up to £100 each after the insurer admitted they had been overcharged on their premiums.

The affected customers had originally taken out policies with Friends Life, an insurer bought by Aviva in 2015.

Income protection, critical illness and life insurance policies are those affected. These are 'index-linked' policies, meaning their premiums are designed to change in line with inflation. But an IT error meant some customers were charged more than they should have been.

Aviva says the error could have occurred at a number of stages, though in some cases customers have been overcharged since the first anniversary of their policy. As some affected policies were taken out as long ago as the early 1990s, this means some customers have been overpaying for a number of years.

For more info on different insurance policies, see our Life Insurance and Loan PPI guides.

How will I know if I'm affected?

Aviva says it will write to all affected customers over the next few months.

If you're affected, you won't need to do anything – Aviva says customers will receive the refund automatically "within a number of days of receipt of the letter".

Refunds will be paid by cheque or into your bank account (depending on how you pay for your premium). Premiums will also be adjusted to make sure they're correct.

If you think you may have been affected but you're worried Aviva may not be able to contact you – for example, if you no longer have the policy or have moved house – you can contact Aviva directly.

What does Aviva say?

An Aviva spokesperson said: "As part of an ongoing review of our policies, we've found a number of our older-style Friends Life – now Aviva – customers who have index-linked life insurance policies have paid higher premiums than they should have done.

"Around 50,000 customers are affected with the vast majority overcharged by £100 or less. In some cases, it's a lot less than £100.

"We're contacting all affected customers to apologise and are committed to ensuring they are not financially disadvantaged as a result.

"Following a meticulous investigation, this has now been fixed."