I have a bank account where I deposit my university stipends and stock subscription profits for a period of four years. I am asking about the obligation of Zakat on the stipend and the subscription, or on the subscription only, and whether it is obligatory on the profits only.

All praise is due to Allah, and may peace and blessings be upon the Messenger of Allah, and upon his family and companions. To proceed:

Zakat is obligatory on saved wealth if it reaches the nisab (minimum threshold) and a hawl (one lunar year) has passed over it, whether it originates from bonuses or profits from permissible stocks. As for profit from unlawful investments, there is no zakat due on it, and it must be given to the poor; only your principal capital belongs to you. Details concerning zakat on stocks can be found in Fatwa 30551, and the method for calculating zakat for past years is explained in Fatwa 98644. If it is difficult to ascertain the exact amount due, then act based on your best estimation and give what you are certain of or what you predominantly believe to be due, for Allah does not burden a soul beyond its capacity.