Tithing is not a Biblical requirement for Christians today.
It is true that the commandment to tithe a tenth of the produce of the land was part of the Law that God gave to the 12 tribes of ancient Israel more than 3,500 years ago. (Leviticus 27:30, 32; Numbers 18:21, 24) But the Bible states categorically that the sacrificial death of Jesus, in 33 C.E., "blotted out," or "abolished," the Law and with it the "commandment to collect tithes." (Colossians 2:13, 14; Ephesians 2:13-15; Hebrews 7:5, 18)
Rather than specifying an amount or a percentage, the apostle Paul merely suggested that "on the first day of every week, each one . . . should set aside a sum of money in keeping with his income." (1 Corinthians 16:2, NIV) By planning and reserving an amount on a regular basis, the Corinthians would not feel pressured into giving begrudgingly or on emotional impulse when Paul arrived. For each Christian, the decision of how much to give was to be a private matter, one that 'he had resolved in his own heart.' (2 Corinthians 9:5, 7)
Something else to consider is that the early Church Fathers did not teach tithing:
"The wealthy among us help the needy . . . They who are well to do, and willing, give what each thinks fit."—The First Apology, Justin Martyr, c. 150 C.E.
"The Jews had indeed the tithes of their goods consecrated to Him, but those who have received liberty set aside all their possessions for the Lord's purposes, . . . as that poor widow acted who cast all her living into the treasury of God."—Against Heresies, Irenaeus, c. 180 C.E.
"Though we have our treasure-chest, it is not made up of purchase-money, as of a religion that has its price. On the monthly day, if he likes, each puts in a small donation; but only if it be his pleasure, and only if he be able: for there is no compulsion; all is voluntary."—Apology, Tertullian, c. 197 C.E.
"As the Church expanded and various institutions arose, it became necessary to make laws which would insure the proper and permanent support of the clergy. The payment of tithes was adopted from the Old Law . . . The earliest positive legislation on the subject seems to be contained in the letter of the bishops assembled at Tours in 567 and the [canons] of the Council of Macon in 585."—The Catholic Encyclopedia.
A Religion That Does Not Collect Tithes
Some have expressed surprise when they discover a religion where there are no tithes, no collection plates and no collections are ever taken at their meetings.
The work of Jehovah's Witnesses is primarily financed through anonymous, voluntary contributions, as was true with the early Christians. (2 Cor. 8:12; 9:7)
Any donations from interested persons are used to further the worldwide work of Bible education conducted by the Witnesses.
For more concerning this, see:
How are Jehovah's Witnesses Funded?; Jehovah's Witnesses Official Media Website)
How Is It All Financed? - Not Serving for Personal Gain (Jehovah's Witnesses Questions and Answers; Excerpt from the Proclaimers Book - jv chap. 21 pp. 350-351 How Is It All Financed?)
How is the work of Jehovah's Witnesses financed? (Search For Bible Truths)
For more about tithing, see:
Religion - How Should It Be Financed? Giving That Brings Joy (w02 12/1 pp. 4-7; Watchtower Online Library)