National Disaster Tax Relief Act of 2017 This bill amends the Internal Revenue Code to provide tax relief for federally-declared disasters in 2012, 2013, 2014, and 2015. For individuals and businesses located in or investing in the affected areas, the bill allows: expensing of certain disaster expenses, increased deductions for charitable contributions for disaster relief, modifications to rules regarding the deduction of losses attributable to disasters, waivers of certain mortgage revenue bond requirements, an extension of the additional depreciation allowance for business property (bonus depreciation), an increased new markets tax credit limitation, penalty-free distributions from retirement plans, an additional tax exemption for individuals who are displaced, an exclusion from gross income for certain cancellations of indebtedness, a modified rule for determining the earned income of individuals for the earned income tax credit and the child tax credit, an increased rehabilitation tax credit for buildings, additional advance refundings of certain tax-exempt bonds, disaster area recovery bonds, additional low-income housing tax credit allocations, payments of disaster assistance to tax-exempt mutual ditch or irrigation companies without affecting their tax-exempt status, an exclusion from gross income for disaster mitigation payments received from state and local governments, a deduction for payments to a tax-exempt natural disaster fund, a five-year replacement period for property for purposes of the exclusion of gain from an involuntary conversion, a tax credit for a portion of the wages paid to employees, and an enhanced deduction for medical expenses.