By now, you've probably got used to the new 12-sided £1, and stopped wondering whether you've picked up some foreign cash by mistake.
But the chances are that you've still got some of the old round coins knocking about - and if you do, you'd better get a move on and spend them.
See also: Scammers faking 'error' £1 coins
Since March, we've been in what's known as a co-circulation period, with both old and new £1 coins being valid. But there are now only 100 days to go until October 15th, when the old round coins cease being legal tender.
"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," says Baroness Neville Rolfe, commercial secretary to the Treasury.
And it's not just your purse that you should check. If you have children, the chances are that their piggy-banks will be full of old £1 coins, for example. Meanwhile, many people keep a pot of cash hidden away for emergencies, or collect coins for charity.
You could also check down the back of the sofa; the kitchen drawer where you keep bits and bobs; and the bottom of all your handbags, for example.
"It's worth doing it now, as with piggybanks and coin jars it's all too easy to squirrel money away and forget about it," says Martin Lewis of MoneySavingExpert.com.
So what should you do if you've still got loads of old round £1 coins?
The obvious thing to do is to spend them whenever you get the chance. Any retail outlet should take them right up to the October deadline.
After that, most banks and building societies, including Barclays, HSBC, Lloyds/Bank of Scotland, Nationwide, RBS and Santander, have said that they will continue to accept the old coins. However, they'll only do this for their own customers.
"So if you're left holding old pound coins after they stop being legal tender and your bank won't play ball, opening a new account with a different provider may be the only solution," says Lewis.
"In any event, carting a bag of coins to the bank is likely to be a real faff – particularly if there isn't a branch near where you live. So it's much better simply to spend or save them now."
Before you do, though, it's not a bad idea to take a careful look at each one. Some £1 coins can be worth £20 or more to collectors - the Edinburgh City and Cardiff City coins for example - so it's worth checking out our list of rare £1 coins here.