From wol:
No, Jehovah’s Witnesses do not practice tithing; our work is financed by voluntary donations. What is a tithe, and why don’t Jehovah’s Witnesses practice tithing?
The commandment to tithe, or contribute a tenth of one’s belongings, was part of the Law given to the ancient nation of Israel. However, the Bible makes it clear that this Law—including the “commandment to collect tithes”—does not apply to Christians.—Hebrews 7:5, 18; Colossians 2:13, 14.
So how do you think they could go around this?