Debt Buy-Down Act of 2011 - Amends the Internal Revenue Code to allow individual taxpayers to designate up to 10% of their adjusted income tax liability for the reduction of the public debt.
Establishes in the Treasury the Public Debt Reduction Trust Fund to hold tax revenues generated by this Act for the reduction of the public debt.
Amends the Balanced Budget and Emergency Deficit Control Act of 1985 to require a sequestration of federal spending equivalent to the estimated aggregate amount designated by taxpayers under this Act to reduce the public debt. Prohibits any reduction in social security retirement benefits, veterans benefits, or interest payments on federal debt as a result of any such sequestration.