Do you have to pay for something you did not order?

You do not have to pay for it if you send it back immediately. You cannot keep or consume the item and then refuse to pay for it. This does not apply to the UK. If you have received an item that you had nothing to do with(did not ask for and did not pay for) then this is classed as the fault of the seller and this means the buyer can consume/keep/use without needing to pay for it. The seller will be stealing from any buyer if the seller takes any money from the buyer in these circumstances.