I would like to know if this is permissible, there is a shop that gives a free card to anyone that signs up for it, when you purchase items from that shop you earn points, the amount of points depend on how much you have spent if you have spent a lot you get more points. Over time the points add up and then turn into money which is given as a voucher for you to spend in that shop. Is this ok to do this and spend that money you earn from the points. May Allah reward you

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.

If signing up with these stores is free of charge and so is the card and the store does not charge the customer more than the normal prices of the purchased products in exchange for these cards, but rather makes this offer to encourage and attract customers to buy from the store and compete with other stores, there is no problem in signing up with such stores and benefiting from the points acquired from buying products.