There are only 100 days left to spend paper £20 and £50 notes - and the public are being encouraged to have a root around their homes for any they may still have in their possession.
The Bank of England says there are more than 300 million individual £20 banknotes, and 160 million paper £50 banknotes still in circulation.
People have until the end of September to use their notes or deposit them at their bank or a Post Office, the Bank said.
September 30 is the last day that the Bank's paper £20 and £50 banknotes will have legal tender status.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know...
While the majority of paper £20 and £50 banknotes in circulation have been replaced with new polymer versions, there are still more than £6 billion-worth of paper £20 banknotes featuring economist Adam Smith, and over £8 billion-worth of paper £50 banknotes featuring entrepreneur Matthew Boulton and engineer James Watt, in circulation.
It is a year since the Bank first issued the polymer £50 banknote featuring Bletchley Park codebreaker and scientist Alan Turing.
The Turing £50 completed the Bank’s “family” of polymer notes, with all of its denominations – £5, £10, £20 and £50 – now printed on polymer.
The Bank of England’s chief cashier Sarah John said: “Changing our banknotes from paper to polymer over recent years has been an important development, because it makes them more difficult to counterfeit, and means they are more durable.
“The majority of paper banknotes have now been taken out of circulation, but a significant number remain in the economy, so we’re asking you to check if you have any at home.
“For the next 100 days, these can still be used or deposited at your bank in the normal way.”