The launch of the new £5 note is a fantastic opportunity to cash in. Some of the Polymer fivers, featuring Winston Churchill, have been changing hands for more than £200 on eBay. So do you have a fiver that's worth a fortune?
Banknote collectors are always on the lookout for something a bit unusual. And while stumbling across one of these oddities is usually very rare, the launch of the new note makes the valuable ones far less hard to come by - in fact you may have already taken one out at a cashpoint, or received one in your change.
Collectors are specifically looking for those that come off the press first - with serial numbers beginning AA01, or at the end of the press. They also like sequential serial numbers in a set of notes. In fact, they like these things so much, they are willing to pay handsomely for them.
Loans at Home has discovered a few changing hands on eBay, including an AA01 note that sold for £196, one that sold for £161, one that fetched £215, and one that sold for £227.56
At the moment, your best bet is to keep your eyes peeled for those with prized serial numbers. However, it's also worth looking carefully at any other notes you get your hands on. It's going to be much harder to find a rare one - but not impossible.
They also pay for mistakes. So, for example, earlier this month a five pound note issued in 1980 without a signature sold for £80 at auction. And at the same auction a pair of pound notes without watermarks sold for £55.
Less valuable - but often more fun to collect - are specific issue dates that relate to key moments in history - and special commemorative notes.
The George Best fiver for example, was released by Ulster Bank in 2006, to mark the year after his death. The notes were fully sold out within days, and were changing hands on eBay for as much as £30. Interest has since died down, so you'd struggle to get much more than the face value for the note. However, if you were to wait for another key anniversary, you may find the market picks up again.
So are the notes in your pockets worth hundreds of pounds? It's at least worth checking.