Some small businesses attempt to prepare their individual income tax returns by themselves. For the simplest of situations, that makes sense. However, business or corporate tax returns are a completely different matter. Sole proprietorships and single-member LLCs may still report on schedule C of the Form 1040, but there are lots of opportunities to make mistakes and to miss perfectly legitimate deductions. One mistake or missed deduction can cost you much more than what you might save by not using a qualified accountant and tax advisor.
If your business is organized as a multi-member LLC, partnership, corporation, or S corporation, different tax forms are used. These are more complicated and less straightforward than the individual income tax forms. It takes experience, skill, and continuing education to effectively minimize your taxes.