Is Zakat obligatory on gold that was purchased with an Islamic credit card and sold after six months to be used for buying an apartment?

A credit card backed by a balance is a loan from the bank. The bank is permitted to take a lump sum for administrative expenses (service fee), and this amount does not increase with the amount used. If your card is of this type, there is no harm in buying and selling gold, and the profit resulting therefrom is lawful. This falls under the Almighty's saying: "Allah has permitted trade and has forbidden interest." [Quran 2:275] A condition for buying and selling gold with paper money is immediate possession (al-taqabud) at the time of the contract. However, if the issuing entity of the card takes a percentage that varies with the varying amounts withdrawn, this is usury (riba) and is not permissible.