What forms does a used automobile dealership file for Federal Income tax?

I am a used automobile dealership. The business was formed as a Partnership. I am interested in potentially purchasing real estate for personal use. The mortgage officer I spoke to at my bank said she needed to see copies of my tax returns for this year to prove my income since I am self employed as my primary income source. This is the first time I will be filing taxes for my business on my own. What forms do I need to file?