This is how God has defined His church, and it’s not a 501c3. Also take note what God says about those who change His definition.

D&C (LDS 10:67-69) (RLDS 3) (1833 9) (1835 36) (1844 36)
67 Behold, this is my doctrine—whosoever REPENTETH and COMETH UNTO ME, the same IS MY CHURCH. 68 Whosoever declareth more or less than this, the same is not of me, but is against me; therefore he is not of my church. 69 And now, behold, whosoever is of my church, and endureth of my church to the end, him will I establish upon my rock, and the gates of hell shall not prevail against them.

Mosiah (LDS 26:22) (RLDS 11:126-130) For behold, THIS IS MY CHURCH; WHOSOEVER IS BAPTIZED SHALL BE BAPTIZED UNTO REPENTANCE. And whomsoever ye receive shall BELIEVE IN MY NAME; and him will I freely forgive.

This article brings out how the translators of the King James version of the Bible were pressured to use the word church instead of assembly when translating “Ekklesia”.
Beware Of Translator Bias

There are literally hundreds of churches/assemblies/congregations/groups who believe that the Book of Mormon is the word of God, and that Jesus Christ called Joseph Smith be a prophet:

Here is a review I did on the book Healing the Breach which talks about miracles happening in different churches that believe in the restoration.
Review of Healing The Breach

This book helps to sort out the histories and theologies of the varied churches within the Latter-day Saint movement. More than a hundred different churches, organizations and individuals are discussed in this book.
Divergent Paths of the Restoration

This fascinating volume contains sixteen original essays on different expressions of the Latter Day Saint movement that have emerged since Joseph Smith organized his church in 1830. Included are groups which trace their path through Sidney Rigdon, James J. Strang, Alpheus Cutler or Granville Hedrick. Also included are historic (no longer extant) branches of the movement that were led by David Whitmer, William Smith and Amasa Lyman.
Scattering Of The Saints: Schism Within Mormonism

This is a dynamic list and may never be able to satisfy particular standards for completeness.
List of denominations in the Latter Day Saint movement

Cataloging the individuals, groups, & denominations related to the prophetic calling of Joseph Smith
The Latter Day Saint Movement

God’s church will be governed by the scriptures which are His words, not policies that are not voted on by common consent.

D&C (LDS 42:59) (RLDS 42) (1833 44,47) (1835 13) Thou shalt take the things which thou hast received, which have been given unto thee in my SCRIPTURES for a LAW, to be my LAW to GOVERN my church;

I talk a little of the problems of a 501(c)3 governed church in Bishops are JUDGEs of Israel:

It basically boils down to, that a 501(c)3 organization is not allowed to speak contrary to what it’s master or parent organization, the Fedral government, says. If it did, it could lose all it’s assets. So sadly the LDS / Brighamite church has decided to server mammon, also know as money, instead of God.

3 Nephi (LDS 13:24) (RLDS 5:115) NO MAN can serve TWO masters; for either he will hate the one and love the other, or else he will hold to the one and despise the other. Ye cannot serve God and Mammon [money].

Rock Waterman has writen good articles on the subject also:

The Hidden Reason For The Policy Change On Baptisms
The Real Threat To Traditional Marriage, Part Three: Betrayal

Here are some things that GeraldWThomas said in State Controlled Churches: The 501c3 Deception that I really spoke to me.

The apostle Paul warned against being unequally yoked with unbelievers.

And what concord hath Christ with Belial? or what part hath he that believeth with an infidel? (2 Corinthians 6:14-15)

In Amos 3:3, YAHUAH asked, “Can two walk together except they be agreed?”

Some good articles about the problems of churches using 501c3 tax status:

501c3 Facts
When a Church accepts the 501c3 status, that Church Waives its Freedoms and Rights: 501c3 Churches – EXPOSED
State Controlled Churches: The 501c3 Deception
501c3 What Is It And How Does It Affect You? – Is Your Church Under IRS Code 501c3?
The Government OWNS and RUNS your Church and its Doctrines! 501c3 Tax-Exempt Organizations