How should I work with registration history?

OpenSafely presents a deduplicated current-registration view in the patient model. This supports consistent cohort construction and avoids duplicate rows for people who move between practices.

What to expect

• A patient appears once in patient for their current registration.
• When a patient transfers practice, the patient row is updated to the new organisation context.
• Historical events remain available and linked through the deduplicated patient representation.

For full transfer behaviour, see Practice Transfers and Patient De-duplication.

Study design guidance

• For current population analyses, use the patient model as the authoritative registration view.
• For longitudinal analyses, use stable patient identifiers (nhs_number) and time-filtered event models.
• The patient model does not provide a full historical registration timeline; historical registrations are not exposed as a separate customer-facing model.

Practical SQL pattern

SELECT
  p.patient_id,
  p.organisation_id,
  p.registration_start_datetime,
  p.registration_end_datetime,
  p.is_active,
  p.has_died
FROM explorer_open_safely.patient AS p
WHERE p.is_active = TRUE