Is zakat obligatory on money invested in stock trading funds, and if so, what is its amount, and is it on the principal amount or on the profit, knowing that 2.5% of each check is paid as zakat?

Zakat (definition) is obligatory on shares according to the owner's intention. If one owns shares solely for the purpose of benefiting from their annual dividends, then there is no Zakat on the principal value of the share. Instead, Zakat is due on the dividends, at a rate of 2.5%, after one hawl (lunar year) has passed from the day they were received. As for one who owns them with the intention of trading, they are subject to Zakat on trade goods, and 2.5% of their market value and any profit, if the shares yield a profit, must be paid. If you invested with the sole intention of profit and paid 2.5% of the profits with the intention of Zakat, this is sufficient. It is preferable that you personally pay its Zakat. However, if you invested with the intention of trading, then it is necessary to appraise them at the end of the hawl and pay 2.5% of their value.