Turbo Tax doesn't calculate tax correctly

Correction to prior post:

According to the Instructions for Form 1040, the tax burden (line 16) is based on a formula applied to taxable income (line 15).  For my filing status and income (requiring the formula versus the look-up table) the tax burden computed by Turbo Tax is over $700 less than the amount the formula yields.  In checking last years return, the Turbo Tax computation was over $500 less.  It's simple math.  What gives?