Small Business Tax Fairness Act - Amends the Internal Revenue Code to extend through 2014: (1) the 100% exclusion from gross income of gain from the sale of certain small business stock; (2) the increased amount of the tax deduction for business start-up expenses; (3) the reductions of the recognition period for built-in gains of S corporations; and (4) the increased expensing allowance for tangible business assets, including computer software, and real property. Allows a deduction in 2013 for health insurance costs in computing self-employment taxable income.