Multi-member LLC's taxed as a partnership are limited on what year end the entity can use.
The rules are as follows:
- The majority interest rule
- The principal partners rule
- Least aggregate deferral rule
All of these rules, without going into the technical details, look to the year end of the partners in determining the partnership's required year end. Your required year end is most likely December. An exception to this would be if you made a Section 444 election in which you can have at most a 3 month deferral. However, there is a cost to this which is a deposit that is held by the IRS when the entity is profitable.
So in conclusion, based on your limited facts, I believe you filed a correct tax return since it is doubtful your required year end is September or you made a Section 444 election.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
