In case of expensive purchases you may want a manager approval to validate the orders, Odoo let's you easily set that up.
For this feature to work, go to :menuselection:`Purchases --> Configuration --> Settings` and activate the Order Approval feature. From there you can also set the minimum amount required to activate this feature.
Create a new Request for Quotation
While working on a new RfQ, if the order is made by a user and not a manager and the amount of the order is above the minimum amount you specified, a new To Approve status will be introduced in the process.
Approve the order
If you are a purchase manager, you can now go to the purchase order and approve the order if everything is alright with it. Giving you full control of what your users can or can't do.
Once approved, the purchase order follows the normal process.