If you are a sole proprietorship or single member LLC, you must file your business as a schedule C disregarded entity attached to your personal form 1040 tax return. If your LLC made the election to be treated as an S-corp, you must file a separate form 1120 business return before you file your personal return, and include information from your business on your personal return. If you are a simple partnership (without legal registration), or a multi-member LLC, you must file a partnership form 1065, which will create a K-1 statement for each partner that goes on their personal tax return.
Note that partnership returns are due March 15, not April 15, and there is a substantial late penalty if you did not request an extension.
