There was a time when I considered myself to be Mormon. On September 8, 2010 (about a decade ago) I sent a letter to the Member Records Division of the LDS Church that had the following in it:
I wish you to recognize this letter as a formal request to have my name removed from membership in the “Church of Jesus Christ of Ladder-day Saints” (i.e., the “LDS Church”, or simply “your church”). And I also wish to advise you that henceforth, when asked about my possible membership in your church, I intend to respond that I am not a member.
[I do not believe] …that the President of the LDS Church is the sole spokesperson for God, upon this earth, or that your church is “The One True Church of God”.
Consequently, at this time I feel that continued consent to being listed as a member of your church would be dishonest on my part, and that I need to correct it, out of respect for honesty, and even out of respect for your church, and out of respect for other people, whether or not they are members of your church.
About 30 days later I received back a letter from the LDS Church informing me that they had removed my name from their membership records.
You can also check this site out for more information: http://cesletter.org
Mormon-based Ecclesiastical Authority
Members of the LDS Church like to be able to claim they can trace their priesthood authority from a succession of priesthood holding men that eventually root to Joseph Smith (and according to LDS doctrine, from Joseph Smith to Peter, James, and John, and from them to the Savior). At one time, I also believed Priesthood Authority should be traceable back to Joseph Smith, and tied back to his ecclesiastical authority in some way. I no longer believe that.
I had thought my belief on this had changed on or around the time I wrote the above-referenced letter to the LDS Church in 2010, but I have found evidence that I still harbored at least some of this idea as late as 2013. I don’t think this belief survived much (if at all) beyond that year.