I do not work and I earn my living from the profits of bank investment certificates. I have read that the Zakat in this case is 10% of the profits, is that true?

In the Name of Allah the Merciful the Gracious.

Praise be to Allah, and peace be upon His Messenger and upon his family, companions and followers:

And then: It must be warned, first, that the investment certificates issued by usury banks are part of prohibited transactions, and it must not be dealt with by any Muslim who endeavors to abide by his religion’s principles, and whoever has dealt with any of them, the ruling necessitates on him to restore his capital money back, and gets rid of the remaining sum(s) by donating it to public charities, ad he must repent to Allah of doing that.

As for stock exchanges issued by Islamic banks, their Zakat must be paid as the same as on trade tenders, which is one quarter of one tenth, and not the one full tenth, as maintained by the most correct rulings of people of knowledge. And Allah is The Most Supreme and The All Knowledgeable.