Thousands of stamps will become unusable within months after Royal Mail announced major changes.

The postal service has said that it has "reinvented" the stamp for the next generation.

What are the new stamps and why are they changing?

These new stamps will be similar to the regular stamp featuring the profile of the Queen but will have an added barcode on the right-hand side.

Royal Mail has said that the barcodes are part of a modernisation drive that will enable new services.

These include connecting physical stamps to the Royal Mail app, security features and operational efficiencies.

When will stamps become invalid?

All non-barcoded stamps will be valid for use until January 31, 2023.

After this date, non-barcoded stamps will be treated as insufficient postage.

If not used they can be swapped for the new stamps using a swap-out form available online. They cannot be swapped in-store.

Are any stamps exempt?

Special stamps with pictures on and Christmas stamps will continue to be valid and do not need to be used or swapped.

Christmas stamps going forward will be barcoded but special stamps will remain unbarcoded.

When will King Charles III be on stamps?

Royal Mail has said that it will announce "future stamp issues at the appropriate time".

All existing post boxes will remain unchanged. Only post boxes put in production after the Queen's death will have the King's cypher.