Government Shutdown Prevention Act of 2013

Government Shutdown Prevention Act of 2013 - Declares that, if any regular appropriation bill for a fiscal year does not become law before the beginning of the fiscal year, or a joint resolution making continuing appropriations (continuing resolution) is not in effect: (1) the Secretary of the Treasury shall fully pay principal and interest on the federal debt held by the public; and (2) Social Security, Medicare, and Medicaid benefits shall be fully paid and new enrollees shall be accepted.

Declares also that, if the defense appropriations bill has not been enacted, the Department of Defense (DOD) shall operate at 90% of the level of funding for the preceding fiscal year, except for funding for overseas contingencies in Iraq and Afghanistan, which shall be funded at 100% of the preceding fiscal year levels. Authorizes DOD to pay all military personnel at the full level of pay.

Requires federal employees of unfunded agencies to: (1) report for business as normal; and (2) be paid, when funding is provided, at 75% of their salaries for the time worked while under the requirements of this Act. Requires DOD civilian employees based in the United States also to be paid at 75% for the same period.

Limits Congress and the Executive Office of the President to operation at 50% of the level of funding for the preceding fiscal year during a period that any agency is not funded.

Prohibits Members of Congress and the President from receiving salaries or back pay during the period an agency is not funded.

Requires all other non-personnel accounts not funded by a regular appropriations bill or a continuing resolution to operate at 2/3 of the level of the preceding fiscal year. Dedicates the use of savings from this reduction to reduce the federal budget deficit. Prohibits expenditure of any funds during such a period to: (1) carry out the Patient Protection and Affordable Care Act, (2) pay for any abortion, or (3) be provided to any nongovernmental organization that promotes or performs abortion.