1. In Purchasing, from the Tasks menu, select Enter Change Orders.
2. Enter a change order for the purchase order you want to change.
3. Make the changes on the Purchase order (If you need to remove an item, enter a reversal line).
4. Click Commit to commit the change order.
    NOTE: Once you commit a change order, you cannot uncommit it, and you must enter another change order to make any changes to it. 
5. From the Tasks menu, select Send Po's to Job Cost and click Post.
6. Import the change order in Job Cost (Tools menu, Import, Commitments).

Option 2 – If there are no Change Orders against the Purchase Order.

1. Delete the commitment in Job Cost.
2. Delete the invoice out of Accounts Payable. [BCB:321:Refer to article:ECB] How do I delete an invoice in Accounts Payable?
3. Delete the invoice in Purchasing. [BCB:321:Refer to article:ECB] How do I delete an Invoice in Purchasing?
4. Delete the receipt in Purchasing. [BCB:321:Refer to article:ECB] How do I delete a receipt in Purchasing?
5. In Purchasing, go to enter orders and uncommit the Purchase Order.
6. Make any necessary changes to the purchase order.
7. Commit the Purchase Order.
8. Complete your typical workflow for the purchase.

How do I delete or remove a Job Cost or Project Management commitment?