1) I want to ask, how do I give khums? Am I obligated if I don’t own a business?

2) Could I pay it when I do my taxes, so that I’d be able to tell how much I made in the year from where I’ve worked? And to see how much I spent, I’d have to go back through my transaction history and see how much I spent compared to how much I’ve made, yes? Do cash transactions count if they were so small that I can’t remember them? And when I’ve calculated who do I give it to? Is it like zakat where there are organizations?

1) Khums is not whether you own a business or not. It is paid on the extra surplus each year. Say you make 50 thousand and you spend 40 thousand. The ten thousand is the extra surplus. You would have to pay 1/5 of that, which is 2 thousand. You have to also pick a date to give Khums. You refer to that date every year when you make calculations.

2) If you will do your taxes soon you can do your Khums
Calculation after that.

You don’t need to look at all transactions. Just see what you own after the expenses are taken out.
Then give 1/5th of that which is left. When you are ready I can direct you to organizations that take the Khums.

Also according to sayed Sistani if you have a house mortgage you can deduct it from the Khums. (However it’s not that simple, there is a specific calculation)