115 – Giving a Tenth / Part II, Chapter Eighteen (d)

A person who has a small business and earns only a small amount at a time, such as a grocer, and so he cannot record every small profit for his ma’aser (tithing) calculations – he should do a reckoning once a year of all his profits and deduct whatever expenses he had. He should stipulate a condition from the outset that the ma’aser reckoning will not be exact, but he will base the amount he will give on an estimate.

One takes ma’aser from monies that one inherits, just as he would take from any other financial gain.