Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
For the validity of sale, the sold item must be property of the seller, except for exceptional cases, such as a forward sale (Al-Salam). This condition is true whether the sale is via the internet or otherwise.
Answering your question, The Assembly of Muslim Jurists of America, states:
Conditions of a valid sale
In general, a condition for the soundness of a sale is the sold item must be property of the seller, except for exceptional cases, such as a forward sale (Al-Salam). This condition is true whether the sale is via the internet or otherwise.
The difference between selling something that one does not possess and a forward sale is that in the former case one is selling a particular item that is not his property while in the latter case the one is responsible to provide an item by its description, and that item has to be an easily available or identifiable fungible, such as a specific weight or volume of specific types of seeds or number of new cars with specified details or new phones with specified specs.
There is a difference of opinion in Fiqh as to whether one must take legal possession of an item before reselling it. The strongest opinion is that it is obligatory, in general, to take such possession before reselling the item.
Forms of taking possession of sold items
Possession can actually be a physical possession, such as when one takes something by his hands, or by weight or volume for food, or by transporting or moving the item to one’s protected area. However, possession can also be by consideration and ruling (de jure), or by giving up one’s interest in something, even if there was no physical possession taking place.
The nature of the possession, therefore, differs depending on the nature of the case. People differ in their customs concerning what constitutes possession. Thus, the possession required by the Law will be determined in its details by custom.
Sound ways and means of buying merchandise online
The sound ways and means of buying merchandise via the internet are the following:
- The customary fashion: selling an item after owning it and being fully liable for it.
- Forward sale (Al-Salam): A forward sale is where something is sold based on its detailed description with a future delivery and present payment. The way it would work here is the seller displaying on his website merchandise that he will be able to procure, with a detailed description of it, leaving no room for ignorance as to what the item is. Then the seller purchases the item, with immediate payment, for the one who ordered it, and procures it in any way that he wills.
- Brokerage sale: The broker is the one who deals between the buyer and the seller by concluding the sale or guiding to the means for it, with a fee for his services. The earnings of a broker are permissible if it is known who is going to pay it and if it is free of deceit, deception, or lying.
- Agent sale: This is where the seller is an agent for the seller in selling his merchandise on his behalf for whoever orders them. In return, he receives a stipulated payment.
The most appropriate of those means is the forward sale if all of its conditions are met.
Almighty Allah knows best.
Source: AMJA Online