The Royal Mail has warned customers to "use up or swap out" stamps before they are replaced with barcoded ones.
People have until July 31 to use them up after the postal service introduced a six-month grace period before they can no longer be used.
After this time, if stamps without barcodes are used people will face extra charges in order to receive their mail.
The Royal Mail's Swap Out scheme will continue indefinitely, allowing people to continue to check their purses, wallets and drawers for the old-style stamp and swap for the new ones.
Matthew Parkes, managing director of stamps and collectibles, said: “We don’t want any of our customers to be out of pocket.
“We continue to encourage customers to check their purses, wallets and drawers to find and use their non-barcoded definitive stamps before the final deadline of July 31.
"But even if they miss this date, there is currently no time limit on customers swapping their non-barcoded stamps for barcoded stamps via our free Swap Out scheme.”
The move is part of the company’s ongoing modernisation drive and will allow the unique barcodes to facilitate operational efficiencies.
The change was first announced on February 1, 2022 - giving customers time to use up their old-style stamps.
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