In order not to lose or compromise to some degree the benefits and protections provided by the use of a formal business entity, it is necessary to follow all business and legal formalities associated with the proper maintenance of that entity, whether it be a corporation or LLC.
The information provided in this answer does not create an attorney-client relationship. If you are interested in a free consultation with Mr. Bryans, call The Bryans Law Office at (303) 832-2930.
You are not responsible for the taxes of your LLC Co-Member. You should discuss the delinquency. Sometimes, it is as simple as an annual filing with the Secretary of State and he may be able to easily correct it. If the LLC has payroll tax responsibilities that are not being paid (the LLC, not the S Corp), then you may be responsible for that as such would be considered trust funds. Also, normally one does not file a K-1 WITH a return, but reports the K-1 income ON one's personal return. Also, you DO have an operating agreement. And, it is the one dictated by the State when you fail to make your own. You may not like the terms of that agreement. I encourage you to meet with an attorney to draft an operating agreement. It should address the basic issues of the business and its management.
Marty Davidoff, email@example.com, 732-274-1600. This answer is provided for general information only. You should seek advice from an attorney or tax professional.
Honestly, this is nothing that can be fully addressed on a message board. Why don't you find one of the excellent attorneys on this AVVO website that work with business entities to make sure you are protected? Robert Murillo and Chris Leroi come to mind as possible contact for you.
Best of luck.
In no way am I offering you legal advice, and in no way has my comment created an attorney-client relationship. You are not to rely upon my note above in any way, but insted need to sit down with counsel and share all relevant facts before receiving fully-informed legal advice. If you want to be completely sure of your rights, you must sit down with an experienced criminal defense attorney to be fully aware of your rights.
If you are referring to the secretary of state's notice of delinquency, that simply means that the entity has failed to file an annual report, and if it does not eventually correct this it will be administratively dissolved as a corporation. From this you cannot know whether it actually has a tax issue going on. But clearly you should have an operating agreement that can address these kinds of problems and provides a contractual understanding between you and your partner - for example, an agreement could provide for a forced withdrawal of a member for tax delinquency, bankruptcy and the like. You definitely should have a lawyer help you to draw one up, and also look into any other problems that might be arising, including the tax questions.
This response is not intended to create an attorney/client relationship between any individuals, and is not intended as specific legal advice.