Profits
30. Multiple businesses. If someone has multiple businesses, and he profits from one but suffers a loss from another, or profits initially and then suffers a loss, and he set a specific time to take off maaser (above, 15), he can put all his businesses together, calculate one sum total based on his income and expenses from all his businesses, and then give maaser for the grand total (צדקה ומשפט פ''ה אות ט ').
31. Shares, stocks. Some people buy shares in companies and then sell them after some time. If someone did this as a onetime venture, he should set aside maaser from the profits when he sells the shares. However, if he constantly deals with stocks, buying, selling, etc., instead of taking off maaser every time he sells, he can make a calculation of what he made versus what he lost at the end of the time period he set for himself, e.g. half a year or one year, and take off maaser from his net profits (הגר''נ קרליץ, באורח צדקה פ''ט אות ב ').
32. Gifts. If one received items as gifts, e.g., on the occasion of his marriage, he does not need to use money he received as maaser for the cash value of items he received. However, if he received money, he must set aside maaser (שו''ת יד הלוי ח''ב סי' מ''ד ). If he received checks, he must use cash as maaser for them.
33. Apartment rental income. Someone who rents out an apartment must take maaser off the rent he collects. If he also pays rent for the apartment he lives in, he only needs to take off maaser for rent money he collects in excess of what he personally pays for rent (מו''ר שו''ת שבט הקהתי ח''ו סי' של''ד ).
34. Stolen item that was returned. If something was stolen from someone and then returned, he does not need to give maaser from it. If, however, money was stolen from someone and then returned to him after he had given up hope of recovering it, he must take maaser off that money (שו''ת צי''א ח''ו סי' כ''ו ).
