Protecting Our Students and Taxpayers Act of 2013 or the POST Act of 2013 - Amends title IV (Student Assistance) of the Higher Education Act of 1965 to require proprietary institutions of higher education to derive at least 15% of their revenue from sources other than federal funds or become ineligible for title IV funding. (Currently, the 90/10 rule requires these schools to derive at least 10% of their revenue from sources other than title IV or become ineligible for title IV funding.)

Defines "federal funds" as federal financial assistance provided through a grant, contract, subsidy, loan, guarantee, insurance, or other means to a proprietary institution, including federal financial assistance that is provided to an institution on behalf of a student or to a student to attend the institution. Excludes monthly housing stipends provided under the Post-9/11 Veterans Educational Assistance program from consideration as federal funds.

Limits what a proprietary institution may treat as revenue to the school in calculating whether it derives at least 15% of its revenue from non-federal funds.