How to close Purchase Order at 400-400 status

Dear All,

User has created a PO for quantity 300. Through EDI, received quantity 288, 12 and 20. I see 3 lines in F43121. Quantities 288, 12 are moved to stock. Excess quantity, user has P4314, did PO receipt reversal. In F4312, I see lines at 400-400, qty order=300, Qty received=300, no open quantity. what is the best way to close the PO from front application, not using SQL update.

Please let me know if you have any questions.

Thanks