1. Device alerting to the expiration of tariffs for a franking system, comprising a random access memory (RAM) for recording postal data including: a first table of postal tariffs relative to postal products and services and a processing unit for updating these postal tariffs, wherein said RAM further comprises a second table of postal tariffs and said processing unit comprises means for comparing said postal tariffs of the first and second tables and for emitting to the operator of the franking system a message alerting to the expiration of tariffs when a date of application of said postal tariffs of said second table is identical to or earlier than a desired date of franking and when one of said compared postal tariffs has been changed.