Federal income taxes are not deductible. Similarly, you cannot deduct your payment of FICA on wages or the additional Medicare taxes on earned income (0.9% over your threshold amount) and net investment income (3.8% if your adjusted gross income is over a threshold amount). However, the 2014 payment of 2013 federal income taxes is credited to your 2013 return; any excess payment can be refunded to you or applied toward your 2014 federal tax liability.
This is generally adjusted gross income increased by certain items such as tax-free foreign earned income. MAGI usually is used to determine phaseouts of certain deductions and credits.