We're all familiar with the shiny 12-sided £1 coins, which entered circulation at the end of March and have slowly been making their way into the pockets of people across the country.

However, many people are not yet aware that the old round coins will cease to be legal tender on 15 October 2017.

After that date, any unspent £1 round coins can be traded in at banks, but this is only a temporary option – so it is a good idea to spend or exchange these old coins now to avoid not being able to in future.

The Royal Mint said: "We would encourage you to spend, bank or donate your round £1 coins before October 15."

The 12-sided one pound coin entered circulation on March 28, replacing the familiar round £1 coin, which has been in circulation since 1983.

The new coin has been called “the most secure in the world” and there are more than 1.5 billion of them in circulation. About one in 30 of the old round £1 coins in circulation is a counterfeit.

All coin handling equipment, such as vending machines, car park ticket machines, leisure centre lockers, supermarket trolleys and self-service checkouts, should now accept the new £1 coins.

If you're still being handed back old £1 coins in shops and supermarkets, you have the right to ask the cashier to give you a new £1 coin – if they have any – instead. But businesses don't have to comply.

A spokesperson for The Royal Mint said: “We have urged businesses and their frontline staff to, where possible, prioritise the new coin when giving customers their change.

"Customers are entitled to ask for their change in any way they wish, but until October 15, businesses can continue to give out the old coin.”

From 11.59pm on October 15, businesses are under no obligation to accept the round £1 coin from customers, so the best thing to do is take any old pound coins to a high street bank, if you have an account with them, or the Post Office.

But do call your bank first to check whether they are accepting the old pound coins to avoid a wasted journey.