The new £1 launches on 28 March - but all old coins need to be spent by 15 October, the Treasury said today. The Royal Mint is currently cranking out 2,000 of the new coins a minute (that's 3m a day) in preparation. Come October, 1.5bn of the new coins - dubbed the world's most difficult to counterfeit - will have gone into circulation.
But that leaves the thorny question of what to do with the old £1 coins still kicking around. Figures suggest in London alone, 70m of the coins are stashed away.
The Treasury said today people either need to spend them before the launch date, or return them to their bank so they can be melted down and reused.
Other than the difficult-to-copy 12-sided shape, the new coin includes a hologram and a hidden "high security feature" which can be detected "at speed", as well as micro-lettering and "milled edges" - grooves on alternate side.
The bi-metallic new coin will be thinner, lighter and wider than its predecessor, and include the fifth coin portrait of the Queen.
“It’s been over 30 years since the old round pound was first introduced and it seems a fitting send off that many of the coins that are returned will be melted down and reused to make the new coins," said the Royal Mint's deputy master and chief executive, Adam Lawrence.
Here's hoping the new coin won't be faced with the same fiasco as the new plastic fiver, which was slated by vegetarians after they discovered it contains trace amounts of tallow, an animal fat.
Earlier this month the Bank of England said after a consultation, it had decided not to take the notes out of circulation, because it had spent £46m reprinting them.