Bank of England notes out of circulation
If you have a £50 note anywhere check it now: if the face that features on it is Sir John Houblon then you only have until Wednesday to spend it.
It said that it was not unusual for notes to remain in people's hands after they ceased to be legal tender. Almost four years after the £20 Elgar note was withdrawn, the Bank said it believed 80m worth £1.6bn were still outstanding.
After Wednesday only the £50 note featuring Matthew Boulton and James Watt, which was introduced in November 2011, will hold legal tender status.
Anyone holding Houblon notes should be able to pay them into a deposit account held at a bank or building society.
Barclays, NatWest, RBS, Ulster Bank and the Post Office have all agreed to exchange the notes, up to the value of £200, until 30 October 2014.
The offer of an exchange extends to every note ever issued, although in some cases consumers would be better off contacting a dealer rather than the Bank. While an exchange will get you 50p for a 10 shilling note, they are selling on eBay for at least three times that amount.