A business expense is a cost of conducting business. It is in your best interest to deduct legitimate business expenses. It is not in your best interest to deduct expenses that might flag you to be audited. If you are just starting out, it may help you to hire an accountant to help you understand the tax laws, to help you set up your books, and to help you configure and file quarterly taxes. Common expenses that may be deductible include employee pay, lease payments, interest paid, taxes, insurance payments, travel and mileage, utilities, business services and technology purchases.