If I invested money and realized a loss, do I deduct this loss from future income in terms of giving maaser from it.
Example: I made $10k, gave $2k to maaser. Invested the remaining $8k and lost it. I then make another $10k. Do I now only give maaser on $2k?
Thank you for your question.
According to most poskim, the way that you should calculate maser is by calculating not only the gains but also the loses, because the loses are part of the overall business. Maaser is calculated on a yearly level, therefore if you made 20k in total after the year is over subtracting the loses from the gains, then you only give maaser on only 20k. This would be 2k. This applies even if you already gave maser before making the calculation. If you gave more than what you earned during the first part of the year, you can still calculate it towards the yeats maser money.
In the zechus of tzedakah, Hashem should send you an abundance of parnassa
Leket yosher 2- Y:D pg. 76, Pischei Teshuva Y:D 249-1, Noda B’yehuda2-194, Shevet Halevi 5-133-(9), Igros Moshe Y:D 1-143, although it should be noted that R’ Moshe writes that one who wishes to do extra will only count the gains and not the loses. Additionally, see Shvus Yackov 2-86 says that if the deals were made at separate times, that they should not be counted as one. However, as stated, there are a number of poskim who say that the different investment can be counted into one calculation.