Your spouse cannot become an LLC member automatically, even though the LLC might qualify as marital property that belongs jointly to you and your spouse, and even though you and your spouse report LLC income on your joint tax return.

LLCs have formal operating requirements, which govern how new members can be admitted (among other things). This is true whether the LLC has drafted its own operating agreement or is subject to state default rules that apply in the absence of an operating agreement. When your spouse becomes a new member, you'll need to follow the rules that apply to your LLC.

At the very least, you'll have to make a written record of the decision to admit your spouse as a member. In addition, if your LLC operates under an operating agreement, you will probably need to amend the operating agreement to reflect the capital, profits, and voting interests of the new member and the changes in the existing members' interest.

  Don't set your spouse's capital rights and voting rights at zero. If you do, a court or the IRS might call the membership a sham.

Once your spouse is a member, you will both report LLC income on your personal tax return. Both of you will pay quarterly estimated income taxes and self-employment taxes. Plus, you have to carry out the LLC formalities for member voting according to your operating agreement (if you have one) or under state law.