You must have the Patient Merge permission to undo a patient's account merge.
Undoing a merge will reactivate the merged patient account and transfer the applicable financial data, activity, notes, documents, and appointments from currently opened patient account to the original patient account.
Select Patient > Patient.
Use the Search field to search through your patients.
Select the Patient.
Click the Merge button found at the top of the page.
Select Undo Merge.
The Patient Merge window will show all patients currently merged.
Check the box next to the patients you want to unmerge.
Click Undo Merge.