So your DBA business requires a separate tax return. It sounds like with you splitting the profit with your sister that you have a partnership. It also could be a S Corporation operating as a partnership. So you (the DBA partnership) will need to file a Form 1065 Partnership return for both the Federal and State returns. Both are due March 15 of each year. Part of the return is the Schedule K and Schedule K1. You and your sister would get a Schedule K1 to report the profit from your business dba.
Now who is required to file the partnership return? That is usually addressed in the partnership agreement. Depending on the size of your business, you may want to talk to a tax professional. Unlike a Schedule C business for self employed individuals, you business return will also have a balance sheet and other business related forms. Your business may also be subject to other state and local taxes.
I hope this answers your question. It appears that you were thinking that you or your sister would have to file something like a Schedule C on your return. As you can see its a little more complicated. My advise is if the person who helped set up your DBA business is not a tax expert that to go to a tax business for help. They may want to file an extension for your DBA and your personal returns.
