If the line item is not posted:

  1. Open the line item
  2. Change the unit cost, quantity, or GL Distribution
 

If the line item is receipted and/or posted:

  1. Delete the original line item [Version 7]
  2. Add a new line item with the correct quantity, cost, or GL Distribution
Reversing entries for the original line item post the the General Ledger, along with the new entries.