Is it better to file a small business separate or jointly filling married.

[CathiM]

If your business is a single member LLC or sole proprietor, you should report it on Schedule C of your Married Filing Joint return. The exception to that is, if you have elected for file as an S Corporation or C Corporation, then your business will file its own return; Form 1120-S for S-Corp and Form 1120 for C Corp.  

A multi-owner LLC is automatically taxed as a partnership by default and files Form 1065.  

However, a single member or multi member LLC can elect to be treated as an association taxable as a corporation by filing Form 8832, Entity Classification Election. And, once it has elected to be taxed as a corporation, an LLC can file a Form 2553, Election by a Small Business Corporation, to elect tax treatment as an S corporation.

A sole proprietorship is a unincorporated business owned by one individual.