Every type of order action will have an effect on the inventory of your store.
Types of order action such as normal orders, pre-orders, partial payments, and full payments.
This article explains whether there will be a reduction in stock or not on every order process that occurs in your store.
If fulfillment is activated, any partial or full payments will automatically reduce the inventory of the particular product in transaction from your store.
If fulfillment is deactivated, there won't be any automatic effect on inventory when there is any partial payment or full payment order.