Millions of £5 notes in circulation will lose their status as legal tender on Friday after the Bank of England released a polymer replacement.
Around 150 million paper notes, featuring an image of prison reformer Elizabeth Fry, are still in circulation but 5 May marks the last day it can be used.
After this date, shops will be under no legal obligation to accept the note as payment.
However, the Bank of England said some banks and building societies may still accept the note and should exchange it for a new one - although this will be at the discretion of each bank.
The Post Office has said its branches will accept the notes as a deposit into any main UK bank account after the deadline.
Martin Kearsley, banking director, Post Office, said "We offer free cash withdrawal and deposit services for customers of all main UK banks.
"We'd like to reassure people that there's no end date to depositing paper £5 notes into bank accounts at local Post Office branches, we will still accept them after the 5th of May deadline."
Barclays also confirmed it would accept the note although a spokesperson said: “We would recommend that customers allow sufficient time to return old notes/coins rather than leave it until legal tender status is withdrawn."
A number of other high street banks confirmed they would either allow the deposit of the old £5 or would swap it for a new note, including Nationwide, Natwest and Santander.
The new polymer £5 bank note was first issued in September 2016.
The new note is stronger than its predecessor and boasts new security features making it harder to counterfeit.
But it has been controversial as it emerged that traces of animal-derived additives were used in its production.
A public consultation has been launched by the Bank into how it produces new £20 polymer notes.
The Bank previously said it has held off signing supply contracts for the £20 polymer note, which is due to be released in 2020, in order to better understand "the range of public opinion" surrounding the use of tallow in bank note production and explore potential plant-based substitutes such as palm and coconut oil.
In September this year, the Bank will issue a new £10 polymer note featuring author Jane Austen.