Mail preparation system

In a method of preparation of a series of mail items in which postal indicia (18) are printed on the mail items (16) when creating an indicium for a mail item after the first mail item, a determination is made as to whether an indicium created for a previous mail item in the series has not been used for example because the mail item was spoiled or removed. If a previously prepared indicium remains unused, a substitute indicium is created. The substitute indicium is a modification of the unused indicium and contains an indication (39) that it is a substitute indicium.