The note, which was first introduced in 1999, has been gradually replaced by the Adam Smith £20 since 2007 and been slowly taken out of circulation since the start of the year.
In the past two months, the number of Elgar banknotes in circulation is estimated to have fallen from 150 million to 125 million. There are about 1.5 billion £20 notes in circulation.
For any retailers who take the Elgar note after June 30, most banks, building societies and post offices will accept the note for deposit to customer accounts and for other customer transactions. The Bank of England will also give value for the notes.