How do I pay Zakat on gold that I sold after one or two years, knowing that I had not paid Zakat on it because I thought that white gold was not subject to Zakat?

White gold is known gold after some materials have been added to it. Zakat is obligatory on it if it reaches the nisab (85 grams), either by itself or by combining it with other gold. The amount of zakat to be given is a quarter of a tenth (2.5%), and it can be given as gold or its cash equivalent according to its market price. Zakat for past years must be paid by calculating the amount of gold at the end of each year.