In order to access primary care services in Northern Ireland, patients need to register with a GP practice. Registrations can be divided into different types: first registrations, transfers from other parts of the UK, migrant registrations and service related registrations. Individual registrations will be deducted from the index of registered patients for a number of reasons including notification of death, emigration, returning to their home country, moving to Great Britain etc. There may be a lag between a patient presenting themselves at a GP Practice and completion of registration. This lag may be greater for patients who have to provide additional documentation as proof of entitlement to services. Similarly for deductions, there may be a lag in removing individuals from the index of registered patients. Given the sensitive nature of the data, this dataset is primarily used to identify patient populations and facilitate linkage to other datasets. Some variables may be provided in aggregated format, for example age may be replaced with age band and postcode replaced with higher level geographical classifications. GP Cypher codes and Practice numbers will not be provided.