Because of First Amendment religious freedom concerns, Congress has never passed any statute anywhere which defines what a church is (beyond saying "a church or convention or association of churches", which is like saying that the definition of a duck is "one or more ducks"). The IRS, which apparently is unconstrained by the First Amendment, has nonetheless ventured where angels fear to tread, and has established criteria which, in its view, define a church as follows:
1. A distinct legal existence
2. A recognized creed and form of worship
3. A definite and distinct ecclesiastical government
4. A formal code of doctrine and discipline
5. A distinct religious history
6. A membership not associated with any other church or denomination
7. An organization of ordained ministers
8. Ordained ministers selected after completing prescribed studies
9. A literature of its own
10. Established places of worship
11. Regular congregations
12. Regular religious services
13. Sunday schools for religious instruction of the young
14. Schools for the preparation of its ministers.
The Tax Court, which is apparently unconstrained by the IRS administrative criteria, has adopted its own view, consisting of most of the same criteria compacted into 7 or 8 points. See, e.g., Pusch v. Commissioner, 39 T.C.M. 838 (1980) or Chapman v. Commissioner 48 T.C. 358 (1967). In any event, not all of the 14 criteria must be met by every individual church, since only a substantial denomination will meet all of the criteria, and the IRS must allow for the existence of independent churches. Thus, there is substantial "wiggle room."