Disability Insurance Protection and Fraud Prevention Act of 2015

Disability Insurance Protection and Fraud Prevention Act of 2015 Requires the Inspector General of the Social Security Administration to increase the number of cooperative disability investigative units to 54 and distribute them equally among the most densely populated areas. Prohibits the Commissioner of Social Security, in determining whether an individual is under a disability for insurance benefit payment purposes, from considering: (1) an individual as approaching advanced age unless he or she has attained age 58; (2) an individual as having attained advanced age unless he or she has attained age 61; and (3) the individual's inability to communicate in English as a vocational factor. Amends titles II (Old Age, Survivors and Disability Insurance) (OASDI) and XVI (Supplemental Security Income) (SSI) of the Social Security Act to eliminate consideration of the combined effect of impairments in disability determinations. Makes appropriations for continuing disability reviews for FY2016-FY2020. Directs the Commissioner to assess for Congress after FY2018 the amount of savings attained as a result of such appropriations in the federal disability program under the OASDI and the SSI programs. Requires the Commissioner to describe for Congress the designs of: (1) a disability demonstration program, (2) a state demonstration program to revise specified existing funding streams for specific populations to improve outcomes and reduce participation in SSI or Social Security disability insurance, and (3) a demonstration program that encourages employers to reduce the incidence of disability among their employees by 20% through a voluntary program that provides the employers with a tax credit if their employees do not file for Social Security disability insurance.