Seniors Affordable Housing Tax Credit Act This bill establishes a tax credit for states to allocate to taxpayers who rent properties to low-income seniors using a rental reduction agreement. Under a rental reduction agreement, the rent and utility payments for an eligible senior unit must be equal to the lesser of: (1) 30% of the monthly family income of the residents of the unit, or (2) the applicable standard fair market rent for the unit. An eligible senior unit must have family income that does not exceed the greater of: (1) 30% of the area median gross income, or (2) the applicable poverty line for a family of the size involved. The unit must also include at least one occupant who has attained the age of 55 at the beginning of the lease