Partial delivery often arises when the production is finished for specific items you want to ship out, but the production for all required items still needs to be completed.
If you are making products to order and want to deliver products partially when certain items are completed, you can partially complete manufacturing and ship out the products.
Since there's a more vital link between the Make-to-Order (MTO) MO and the SO, You can partially deliver the quantity that is partially completed on the MTO.
The completed items can now be selected to deliver the SO partially.
Read more about partially completing Manufacturing orders.
Once an MTO is partially completed, you cannot change the SO quantity to less than the Completed quantity of product completed by the MTO. If you need to change the SO quantity to a smaller amount, you can revert the partially complete MTO and change the SO amount.