They have been in circulation for the past 34 years and more than 1.6 billion of them have been minted, but from midnight they will cease to be legal tender.
However, 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.
The new 12-sided pound coin went into circulation in March and has new high-tech security features designed to thwart counterfeiters.
Image: The new 12-sided pound coin went into circulation in March
Of the big supermarkets, Sainsbury’s has already made the switch to the new coins, both at the till and with its trolleys, while Tesco says it will accept the old coins, but for a further week only.
As for small businesses, the advice to them is to be prudent and understanding.
Alan Soady, of the Federation of Small Businesses, told Sky News: “We know that there will be consumers who miss the deadline who, in the coming days, do turn up at shops and so on and try to spend the old ones.
“There’s no obligation beyond the deadline for businesses to accept them, (but ) in reality, some businesses may choose to use their discretion.”
Video: Know your way around the new pound
Among other organisations that are prepared to extend the deadline are The Royal British Legion. It will allow members of the public, until Remembrance Sunday, to buy poppies with the old pound coin.
Shane Crowhurst, head of the Poppy Appeal, told Sky News: “If you place that round one pound coin into on of (our) tins, we will ensure that pound goes to great use for our beneficiaries and every little bit helps. That’s right up to Remembrance Sunday and I’m sure if you were to present one to the Royal British Legion on the Monday, we’d accept that too.”
:: Everything you need to know about the new pound
Video: New 12-sided coin to replace old pound
High street banks and post offices will also continue to accept the old coins on the condition that they are paid in to customers’ accounts.
Members of the public have managed to get rid of around 60 million coins in the past week alone, but a further 450 million are thought to remain in circulation.
Oh, and as a word of warning, if you find an old pound coin after the deadline, down the back of the sofa or in a half-forgotten piggy-bank, then be careful what you do with it.
Vendors are within their rights to decline them if you try to spend them, but if you knowingly use one in a vending machine, you will potentially be breaking the law by committing fraud.