How to edit a detail using the Details Items/Taxes screen on Sage 300 Purchase Order
Steps:
On the Detail Items Taxes screen, use the navigation buttons beside Line Number field to display the detail line you want to change.
Make the changes you need. You can change a tax class to another tax class that is assigned to the authority, and you can change the choice for the Tax Included option (if the tax authority permits tax-included costs).
Note: You can change item details only until you post the credit note or debit note.
Click Save.
When you are finished, click the Close button or press the F9 key to return to the Credit/Debit tab.