A system for verifying an operation in particular one that includes payment, the system comprising at least one terminal (11) and a plurality of portable objects (10) which may be coupled, preferably without contact, to the terminal. The terminal emits repeated interrogation messages suitable for triggering reading of the contents of a shift register (60, 190) in a portable object when said object is coupled thereto, only after a comparator has verified concordance between first validity data from the portable object and check data from the terminal. After processing, the terminal re-writes updated useful data in the register. Re-writing is only authorized after a comparator (240) has verified concordance between second validity data stored in the shift register with check data transmitted by the terminal into a register (220) of the portable object. The check data is produced by the terminal after decoding the validity data contained in the message derived from reading the portable object (10).