If you have any of the old five pound notes - under the mattress, perhaps, or down the back of the sofa - then spend them quickly.
Because next Friday, 5 May, is the last day on which the paper notes will be legal tender.
After then, shops will be able to refuse them as payment.
Around 155 million of the notes, featuring prison reformer Elizabeth Fry, are still in circulation.
They will not become worthless, however, after next week's deadline.
The Bank of England will exchange them forever - in line with its policy on any note that has expired.
The Post Office will take them too - as payment, or to be deposited into an account.
High Street banks will also accept the old version.
The new plastic note, which was first issued last September, has been the subject of controversy because tallow - a rendered form of beef or mutton fat - was used in its production.
The Bank is consulting the public on the production of new £20 polymer notes, due out in 2020.
Plant-based substitutes for tallow such as palm and coconut oil are being explored.
This September, meanwhile, the author Jane Austen will feature on a new £10 polymer note, recognising "her universal appeal and enduring contribution to English literature".
There is another issue the Bank might wish to consider when signing off the new £10 and £20 notes.
The latest £5 note features a quote from Sir Winston Churchill: "I have nothing to offer but blood, toil, tears and sweat."
On the note, however, there are no quotation marks, and no full stop, causing further controversy.
Professor Alan Smithers, from the University of Buckingham, told the Telegraph that we are "living in a post-punctuation world".
But the chair of the Royal Society of Literature, Lisa Appignanesi, doubted the lack of punctuation would have bothered Britain's wartime leader.
"The eminent Winston Churchill might have wondered why he was on a mere five pound note and not something a little weightier," she said.