D&C 119:4
4 And after that, those who have thus been tithed shall pay one-tenth of all their interest annually; and this shall be a standing law unto them forever, for my holy priesthood, saith the Lord.
The Board of Directors at the COB have cynically manipulated and twisted this verse to their financial advantage and to the disadvantage of the members struggling to feed and educate their children. They have deliberately twisted "interest" to mean "income" when it means nothing of the sort. Interest very specifically means the money you gain over the principal investment. For example, if you invest $100 in a fund, and at the end of it you receive $110, your interest in dollars is $10, not $110.
In this lesson manual, they've twisted interest and made it to refer to both interest and principal investment:
http://LDS.org/ldsorg/v/index.jsp?hideNav=1&locale=0&sourceId=b2a6a41f6cc20110VgnVCM100000176f620a____&vgnextoid=198bf4b13819d110VgnVCM1000003a94610aRCRD
Discuss the following attitudes and decide on the right solution:
1. A man once said, “I pay tithing on all my salary after deductions, since I don’t get the money that is taken for taxes.” Is he correct? (Tithing is one-tenth of all our interest or increase, before anything else is taken out. See D&C 119:4.)
This is so dishonest that it almost rises to the level of fraud. They make the discussion about paying tithing based on gross or net income, when in fact the scriptural basis for tithing is 1/10th of interest only.
In other words, an honest and forthright tithing is the following:
Gross Income
- Taxes
- Deductions
- Rent/Mortgage
- Grocery
- Electricity/heat
- Misc non-discretionary expenditures
The resulting figure is your annual interest, of which, as a Mormon, you're obligated to pay 10%. It's not 10% of the principal. The brethren are robbing the Latter-day Saints. There is no nicer way to put it.