There is no way to change a tariff or stock item that has been billed.
Instead, the tariff/stock must first be cancelled and then the correct tariff/stock re-billed to the account.
In order to cancel a tariff or stock item that has been billed to an account, follow these simple steps:
Click on Patient
Click on Patient Administration
Click on Patient Transactions
Click on Billing Transactions
Click on Cancellations
The next window will allow the user to have ALL transactions listed (and they can then find the transaction they wish to cancel) or they can narrow the search by entering a date, location or type.