Do Mormons really pay 10 percent of their income to the Church? (Tithing)

Yes, and with joy, and often they give much more than that.  In addition that ten percent, called tithing, there are fast offerings, and other donations made to charitable causes to help sustain the Mormon Church’s missionary program and its humanitarian work throughout the world.   That does not even take into consideration the countless hours that Mormons donate to the Church through service projects and Church assignments.  Unlike most churches, the Mormon Church has no paid clergy in its congregations, so every job from being a bishop, who presides over each congregation, to Sunday School teacher, to vacuuming the chapel on Saturday is done by the members. 

Tithing is a free-will offering made to help support the Church.  Since no clergy is paid, the money goes to help build chapels and temples and other places like visitors’ centers.  Tithing money also goes to help print copies of the Book of Mormon and other Church educational materials, much of which is distributed either free or at cost.  With a membership of 12 million, it can be expensive to build chapels, repair old ones, and print materials in dozens of languages for members throughout the Globe, but tithing is the main source for that income. 

The Doctrine and Covenants, which contains the revelations of God to modern Prophets explains tithing very clearly:

And this shall be the beginning of the tithing of my people.  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 (D&C 119:3-4).

The scriptures further promise that those who pay their tithing with be greatly blessed.  Abraham paid tithings to Melchizedek (see Genesis 14:20), and Moses commanded the Children of Israel to pay tithes as part of the Law (Numbers 18:24).  The prophet Malachi in the Old Testament compared not paying tithing to robbing God:

Will a man rob God? Yet ye have robbed me. But ye say, Wherein have we robbed thee? In tithes and offerings.  Ye are cursed with a curse: for ye have robbed me, [even] this whole nation. Bring ye all the tithes into the storehouse, that there may be meat in mine house, and prove me now herewith, saith the LORD of hosts, if I will not open you the windows of heaven, and pour you out a blessing, that there shall not be room enough to receive it.  And I will rebuke the devourer for your sakes, and he shall not destroy the fruits of your ground; neither shall your vine cast her fruit before the time in the field, saith the LORD of hosts (Malachi 3:8-11).

Jesus commanded the payment of tithing.  When he was rebuking the scribes and Pharisees for hypocrisy, he noted they were careful to pay their tithes, but neglectful of the more important things like faith and mercy.  Nevertheless, the says that they should do both:

Woe unto you, scribes and Pharisees, hypocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier [matters] of the law, judgment, mercy, and faith: <b>these ought ye to have done</b>, and not to leave the other undone (Matt. 23:23)

Fast offerings are given whenever you fast which means to abstain from food and water for a set period of time (usually 24 hours).  Most Mormons fast once a month and give a fast offering at least equivalent to the cost of the food they would have eaten.  People are encouraged to give much more.  The money from fast offerings goes strictly to help the poor and needy.  It helps pay for food and clothing which the Church distributes to others.  Members can also donate money to other worthy causes in the Church such as supporting missionaries, humanitarian projects, and so forth. 

Mormons do not view these as burdens, but as blessings.  Mormons believe that everything belongs to God and that He allows us to use it so whatever we have is in reality a blessing from our Heavenly Father.  Since everything is His, we give a small portion of it back to help run His Church and to bless the lives of others.  The way Mormons pay their tithes and offerings is different than in some churches.  There is no collection plate or box.  Instead, envelopes are provided in every chapel.  To pay tithing, you simply take the envelope, put the money or check in it, fill out the form in the envelope so they know whether it’s tithing, or for humanitarian work, and then finally seal the envelope and give to the bishop of the local congregation.