Bible Answer: This is one of the most often asked questions about tithing.  The net income is what is left after paying taxes. The Bible is clear that tithing is consider the firstfruits: "As soon as the order went out, the Israelites generously gave the firstfruits of their grain, new wine, oil and honey and all that the fields produced. They brought a great amount, a tithe of everything" (2 Chron 31:5).

            A tithe is "firstfruits" and therefore should be given "first" before you give anything to anyone else—that would include taxes. The difficulty we have is oftentimes a person's taxes are taken out first and it makes it seem that the government got the money first. However, a person who pays his taxes later would have gross income at first. So does this mean a person who has his taxes taken out first should give less than the person who has his taxes taken out later, even though they both pay taxes? I should think not. All should give the same. Both should give the tithe on the gross. All the money you earn has personal benefit. We all benefit from the taxes we pay. We enjoy the roads, parks, services, police and especially protection from our military.

            If we tithed on the net that would mean people who pay higher tax rates would give less to God. In most cases, governments have an escalating tax system. That is they increase the tax rate the more we make. So if we gave our tithes after taxes, then the rich would give less to God. I doubt that this would make sense. "He that is given much, much will be demanded" (Lk 12:48). 

            The classic passage on tithe is Malachi 3:10: "'Bring the whole tithe into the storehouse, that there may be food in my house. Test me in this,' says the Lord Almighty, 'and see if I will not throw open the floodgates of heaven and pour out so much blessing that you will not have room enough for it."  Two thoughts about this passage: first, we are to "bring the whole tithe." Not "part" of the tithe. All of it. This would be our gross income. Second: God has promised to "open the floodgates of heaven and pour out so much blessing that you will not have room enough for it." When you believe that God will bless you, then there is no problem in giving the gross.       

            Although you did not ask the question, I want to answer the question about tithing from businesses. First, business should tithe like anyone else would tithe. However, income from business is not always personal profit for the owner.

            Listen to this passage: "Honour the Lord with thy substance, and with the firstfruits of all thine increase" (Prov 3:9, KJV). The word "increase" means "gains". To be fair, it can also mean "revenue." Those are two different meanings. I personally think Solomon meant "gains" because not all "revenue" is a personal benefit to the owner. Depending on your view of the word "increase" will determine the tithe on your business. 

            For sure, businesses should at least tithe on the profits, even if not the gross income. Let me explain why I think profit should be the basis of the tithe and not revenue: the owner of a business only makes money on the profit. He does not make money on every dime that comes into the business.

            For example, if the business brought in a million dollars a year, yet the expenses was one million dollars a year, then he would have no profit. He would actually have no money to give his tithes. Of course, he should tithe on the money he made if he sold his business. And he should tithe on any salary, including benefits he earns. If he gets a car from the business, he should calculate the value of the car and tithe on it. If he gets a vacation from the business he should tithe on the value of the vacation. Any personal income or benefit he gets from the business should be tithed.

            Even though I think there is a good case to be made on tithing off the profit, some business people choose to tithe off the gross revenue. God bless them. They cannot out-give God.

            In the case of our church, we have no "profit" because we are a "not for profit" charity. However, we tithe on the gross income. God has been good to us and has helped us as a church to prosper. If God could do that for us as a church, surely, He can do this for you as a business owner. I doubt you will regret giving God a tithe on your revenue.

Other related article:

•  Is tithing New Testament?