A new 12-sided £1 coin is set to enter circulation on March 28, according to the government.
The gold and silver coloured coin will be made out of nickel-brass and nickel-plated alloy and is said to be the most secure coin produced in the world.
It has several new features which the government say will make it harder to counterfeit.
The old round pound will be used alongside the new until October 2017, when it will lose its legal tender status.
Around a third of the £1.3 billion worth of coins stored in saving jars around the UK are predicted to be the current £1 style - and the public are urged to spend or bank it before October.
Some of the old coins returned will be melted and used to produce the new coin.
Announcing the date when the new coin will enter circulation, 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."
Why will the new coin be harder to counterfeit?
Multiple sides - Its 12 sides make it distinguishable by sight and by touch.
Latent image – It has an image like a hologram that changes from a "£" symbol to the number "1" when the coin is seen from different angles.
Hidden high security feature – A high security feature is built into the coin to protect it from counterfeiting in the future.
Micro-lettering – It has very small lettering on the lower inside rim on both sides of the coin. One pound on the obverse "heads" side and the year of production on the reverse "tails" side, for example 2016 or 2017.
- Bimetallic – It is made of two metals. The outer ring is gold coloured and the inner ring is silver coloured.
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