Royal Mail Great Britain KING CHARLES III  USED STAMP with  Franking Mark  ( New Barcode System!)

Do you leave the barcode on new stamps?
Nowhere on the stamp book packaging did it say 'do not detach barcode) so I assumed it was something I should hang on to so I could track the letter. Now I learn that you have to keep the barcode on if the stamp is to be considered valid- aaargh!Jan 23, 2023