The first three characters of the code should be 'CTG', followed by a two-digit number incremented within the practice of the prescriber each time an eligible prescription is written. The sixth character is an alphabetic check digit. After the numeric component of the codes used by the practice reaches '99', it resets to '01', i.e. the next code allocated by the practice would begin with 'CTG01'. It is possible for a practice to allocate the same six-digit code more than once on the same day, i.e. if 100 or more eligible prescriptions are written. However, the date of prescription forms part of the check digit calculation algorithm, so while eligible prescriptions written within a practice may share a common first five characters, the check digit should change from day to day. |