Unless your contract specifies otherwise your employee will be deemed to have completed the probationary period successfully if you have not actively told them they haven’t. Make a note of start dates and the end of probationary periods and set reminders so you don’t forget. You may want to think about introducing a clause into your contract that specifies that employees will not be deemed to have completed the probationary period satisfactorily until the fact has been confirmed to them in writing even if that is after the end of the 3 month probationary period. You should, however, have a good reason for not being able to hold the final probationary review meeting on time.