The distinctive 12-sided coin will go into circulation on March 28.
The current pound coin will need to be spent or returned to banks by October 15.
Ministers are urging people to check coin jars and money boxes for the estimated £500m in £1 coins being saved at home.
Chief Secretary to the Treasury David Gauke said: “March 28 should be an important date in everybody’s calendar this year - as we will have a new quid on the block.
“This is a historic moment as it’s the first time we’ve introduced a new £1 coin since 1983, and this one will be harder to counterfeit than ever before.
“Our message is clear: if you have a round one pound coin sitting at home or in your wallet, you need to spend it or return it to your bank before October 15.”
The round pound coin has been in circulation since 1983 when it replaced the pound note.
The 12-sided coin is designed to be much harder to counterfeit with copies of the current pound costing retailers millions.
Then Chancellor George Osborne announced the new coin in March 2014 and last year it was announced a design by a West Midlands teenager would be used for the reverse.
The launch of the new coin poses a major challenge for retailers and other organisations which use coin-operated machines.
Helen Dickinson, chief executive of the British Retail Consortium, said: “Through the British Retail Consortium, most major UK retailers have been engaged in discussions and planning with The Royal Mint and Her Majesty’s Treasury since the March 2014 announcement that a new pound coin would be introduced in 2017.
“Our aim is to ensure that the implementation of the new coin runs as smoothly as possible for our customers and staff. Our combined input into the project means we’re confident the new coin will address the issue of counterfeit coins for businesses and the general public alike, and will prove highly secure for customers to use.
“While there will be a natural transition period where some vending systems may only be able to accept the existing pound coin, our industry is committed to ensuring we’re fully prepared ahead of the launch in March.”