It depends on what platform you are on and whether you need the merchant to cooperate with you. For example, on Alibaba, some have a minimum order quantity and set up consignment sales. In this case, you need to inform the merchant and obtain the consignment sales qualification, otherwise you can't bid for one piece.

If it is for resale, you don't have to say it, but some stores have shipping orders and price lists. If you don't need it, you still need to communicate with the merchant. If some stores don't want customers to know which platform or store it is, they also need the merchant to cooperate and not put this information.

You need to judge whether you need to inform the merchant based on your own requirements