I may have made a goof here and want to fix any problems.
I formed an LLC in 2010. In 2010 and early 2011, I paid the LLC's expenses out of my own bank account, using my own checks, and I had no other members in the LLC other than me. For 2010, I filed my own tax return and listed the LLC's expenses that I paid on Schedule C and took a deduction for them. (The business had zero income.) I didn't have a tax ID number for the LLC at least when I started preparing my return and so I didn't list it. I also didn't consider the LLC as having any capital accounts for its member, me, in 2010.
For 2011, I took in another member, got a tax ID number for the LLC, opened an LLC bank account, etc. I have prepared K-1s and the LLC's tax return, on Form 1065. (The business also had zero income that year.) In 2011, I contributed cash and the other member contributed property.
Now, oh no, I looked on the tax ID letter I got and I was to file a Form 1065 for the LLc in early 2011, apparently for the 2010 tax year. I didn't. Drat.
For 2010, can I do what's easiest and is probably the most accurate: filing a Form 1065 for the LLC, listing zero income and zero expenses for the LLC? Or do I need to go back and re-file my 2010 return, listing the LLC's tax ID number, and should the Form 1065 for 2010 reflect the LLC's expenses? That would be more complicated, and I am not sure if it's right (and it would mess up the capital accounts), since the LLC didn't pay anything itself, but I want to be compliant with the law to the letter.