Some believers will tell you that they have "freely" decided to give 10% of their income to their church. In this way they say it is permissible to call their giving "a tithe." But if we believe the Bible to be the standard for life and practice, we need to pay attention to what it says.
Nowhere in the Bible is Christian giving referred to as a form of tithing. On this ground alone, we have no right to call it something the Bible does not. Instead, the Bible refers to Christian philanthropy in simple terms, as an "act of grace (2 Corinthians 8:6)" or "giving!"
In the book of Philippians, gifts sent in support of missions are referred to figuratively using language regarding offerings of the Old Testament (but not of tithes). As we have seen, the New Testament pattern of giving is very much after the pattern of Old Testament freewill offerings. But now there is no literal fragrance from something physically burned at the temple; the spiritual aroma of our giving goes directly to the throne room of heaven.
Christians calling their giving anything other than what it is makes it easy for others to apply stipulations, or legal requirements, where none truly belong. When our financial support to the church is called "tithing," its ties to the Old Testament Law keep it inseparably bound in legalistic regulations, meaning someone can and will place additional rules on your giving.