Business -> Business losses

Can I Write Off My Business Losses Against My Other Income?

If the business is incorporated, the answer to this is no, except for certain dispositions of shares or debt which result in a business investment loss.

If the business is not incorporated, the answer is yes.  For further information, see 

Business investment loss

If I have a small business, do I have to file both a personal and a business tax return?  

Self-employment losses can be carried back 3 years, and can be used to offset other income.