MRG-4 in HL7 v2: A Field Guide to Prior Patient Account Number
Merging the clinical chart is only half the job — if MRG-4 gets ignored, the retiring account number keeps generating charges that never reach the surviving patient's bill.
MRG-4 carries the account number tied to the losing patient record's billing activity, as opposed to the clinical MRN carried in MRG-1. A patient can have one medical record number but multiple account numbers across separate encounters or facilities, so when two patient records merge, the retiring account number in MRG-4 needs to be reassociated with the surviving patient independently of the MRN reconciliation.
What this field contains
Example
This synthetic MRG-4 value, 55219847^^^HOSP^AN, is the retiring account number that needs to be reassociated with the surviving patient's billing record.
Where this trips people up
Clinical and billing systems often subscribe to the same merge feed but read different fields, and MRG-4 is the one billing depends on. If a test suite only validates that MRG-1's MRN gets reconciled, the billing side can pass every clinical test and still leave charges posting against a retired account number, because nothing exercised MRG-4 specifically. Treat clinical-ID and account-number reconciliation as two separate assertions in test coverage, not one.