Britons are being urged to spend their old £1 coins or deposit them in banks as they will no longer be legal tender from midnight on Sunday.
But people should not panic if they miss the 15 October deadline as major banks and building societies and some big stores are giving them extra time to use them.
After Sunday night, the round £1 coins will no longer be in circulation and members of the public have been returning them at a rate of up to 60 million per week.
However, around 400 to 450 million are still lying around in wallets, pockets and down the back of sofas.
NatWest said there has been big rise in the number of its customers offloading their old round pounds.
Image: The new 12-sided pound coin went into circulation in March
In the first week of October the bank received 34.5 million coins, compared to just over 24 million over a week in September. And they were not just limited to one pound coins as people deposited their loose change.
NatWest said more than 5.5 million pound coins were handed in through coin machines, an increase of two million compared with the normal weekly average.
The new 12-sided pound coin went into circulation in March and has new high-tech security features designed to thwart counterfeiters.
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The Iceland and Poundland stores have said they will continue to accept the old round pound until 31 October.
And Tesco has said it will continue accepting the old-style coins for a week after the 15 October deadline.
People can also deposit them into their bank accounts via the Post Office.