The design will feature 12 sides and be ready for use on March 28, after which there will be just more than eight months left for you to spend the old-style £1 coin before they are no longer accepted.
Only for a limited period after October 15 this year will the old one pound coins be able to be deposited at the Post Office and into bank accounts.
The coin was designed by David Pearce, a schoolboy from Walsall who was 15-years-old when his design was chosen out of thousands.
The old pound coin has not been replaced for more than 30 years, but due to its vulnerability to counterfeiting, a new coin has been designed.
Chief secretary to the Treasury, David Gauke, said: "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."
Here are the all important dates:
- March 28 - The new one pound will enter circulation.
- March 28 until October 15 - Both the new and old one pound coin can still be used.
- October 15 - From this date, shops will be under no obligation to accept the old pound coin.
- After October 15 - For a limited period, old one pound coins can still be deposited at the Post Office and into bank accounts.
Key fact about the new pound coin
It has 12 sides.
It has a high security feature built in to protect it from counterfeiting.
The new coin will be lighter, weighing 8.75g.
It is also thinner, at 2.8mm thick.
And is slightly larger than the old coin, measuring 23.43mm in diameter.
It is made of two metals: Nickel-brass and nickel-plated alloy.
It has a hologram image that changes from a £ sign to the number 1 when seen from different angles.
It has micro-lettering on the lower inside rim on both sides of the coin.
It has grooves on alternate side.
Valuable old £1 coins
The rarest pound coin currently in circulation is the Edinburgh £1, according to ChangeChecker , with only 935,000 around.
It is the only £1 coin with a mintage below 1 million and if you have one, you could get around £35 for it online.
It currently has a reserve bid of £35 on eBay, or you can "buy it now" for £100.
The coin is part of a capital cities series which also features Cardiff, the second rarest one pound coin.
The standard Cardiff coin is currently selling for around £25 on eBay.
Also worth more than just a few coins is the 2014 Thistle design, which comes in as the fifth most rare coin with just over 5 million in circulation.
On eBay, the Thistle £1 is currently listed at £11.99.
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