Am I allowed to reinvest interest/dividend income?

Question:

Hi. I understand that in giving tzdaka in the form of ma’aser any profits I have from investments held are subject to ma’aser.

1. I have investments in funds that pay dividends. Since they are funds that are meant to be held over the long term (40 years), my bank has given me the option to automatically reinvest the amount of the dividend back into the fund whenever it is payed to me. Am I allowed to to do this without paying ma’aser on that dividend? If so, would I just take ma’aser on any gains that I may realize upon selling my holdings in the funds?
2. I also would like to know whether cash I find on the street (e.g. 20 NIS bill) is subject to ma’aser. What about finding a shekel?

Thanks for your time and consideration.

Answer:

1. Money that is invested in the bank and accruing interest is not subject to ma’aser until it is taken out, or the investment finishes.  When that time comes you will calculate how much money you put in and how much it is worth when it matured, and give a tenth of the difference.
2. Money that one finds in the street is considered an earning and is subject to ma’aser.  The amount of the money is irrelevant, whether it is 1 or a million shekel.

Sources:

1. B’orach Tzedakah 9-3, in the name of R’ N. Karelitz shlit”a.

2. Sefer Hayirah of Rabbeinu Yonah D:H V’al Timna.