The current £1 coin will become worthless later this year.
The UK Treasury has warned people not to be caught out by the introduction of a new 12-sided coin.
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The new pound comes into circulation in six weeks' time in a bid to beat forgers.
After that, we have just eight months to use up the old ones before they cease to be legal tender.
These are the key dates:
- March 28 - new coin comes into circulation
- October 15 - shops are told not to accept old £1 coins or distribute them in change
- After October 15 - for a limited period, banks and post offices will still allow customers to deposit old £1 coins into their bank account
Baroness Neville Rolfe, Commercial Secretary to the Treasury, visited the Royal Mint in Glamorgan, Wales, today.
She told Wales Online: "The introduction of a new pound coin, the most secure coin in the world, is a historic event.
"The fact this coin is made in Wales makes it even more special as it underlines the importance of the Union.
"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 15 October."
The Royal Mint is producing 1.5 billion new coins.
They are being introduced because around one in thirty £1 coins in circulation is fake.
The new design was created by Walsall schoolboy David Pearce, who was just 15 when he won the public competition.
His design shows the English rose, the Welsh leek, the Scottish thistle and the Northern Irish shamrock emerging from one stem within a royal coronet
On the alternate side, the portrait of the Queen is the fifth to be done during her reign and was done by Royal Mint coin designer Jody Clark.
Key facts about the new coin
- The outer ring is gold-coloured nickel brass
- The inner circle is silver-coloured nickel-plated alloy
- It has an image like a hologram that changes from a £ symbol to the number 1 when seen from different angles
- It is micro lettering on the lower inside rim
- It has milled grooves on alternate sides
- There is a hidden high-security feature to beat counterfeiters.
The size is also changing
- The new coin will be thinner, at 2.8mm.
- It will also be lighter at 8.75g.
- And it is larger at 23.43mm diameter.
Ahead of today's visit, Alun Cairns, Secretary of State for Wales, said: "It is particularly exciting to get a sneak preview of history being made today at the Royal Mint as the new pound coin is prepared for circulation. The presence of the Royal Mint in Wales as the creator of our currency – as well as being a major employer – underlines how central Wales is to the union.
"The Royal Mint is also blazing a trail as an exporter. The UK Government will shortly hold a conference for exporters in Wales, and companies like the Royal Mint are a great example to follow."
This is the first time the £1 coin has been changed in over 30 years.
Around £1.3 billion worth of coins are stored in savings jars across the country, and the current £1 coin accounts for almost a third of these.