Is the described form of sale permissible in Islamic law, wherein it goes through stages of sending specifications, price quotes, a down payment request, supplying raw materials, and the right to reject them or deduct a portion of their price if a defect is found?

If the contract is for a specific commodity owned by the supplier, there is no objection. However, if it is for a commodity described by characteristics and not owned by the supplier, this falls under the category of salam (forward) sale, which is only valid if the full price is paid at the contracting session. The transaction can be rectified by making it a non-binding promise. Some contemporary scholars have deemed this contract permissible by analogy with forms of salam that some jurists allowed even with a delay in both عوضين (counter-values).