When a new patient registers at your practice you must always create a new record, do not overwrite any existing records.
See Adding a New Patient in the Registration Help Centre for details.
Before adding a patient to your system, it is vital you check the patient has not been registered before. The safest way to check is a date of birth search, see Checking the Register. Providing they are not already on the system you should continue. Previously registered patients must be re-registered properly in order to avoid duplication, see Re-Registration for details.