Truth in Budgeting Act - Prohibits (subject to the Line Item Veto Act of 1996) the receipts and disbursements of the Highway Trust Fund, the Airport and Airway Trust Fund, the Inland Waterways Trust Fund, and the Harbor Maintenance Trust Fund from being counted as new budget authority, outlays, receipts, or deficit or surplus for purposes of the Federal budget as submitted by the President, the congressional budget, or the Balanced Budget and Emergency Deficit Control Act of 1985 (Gramm-Rudman-Hollings Act). Exempts such trust funds from any general statutory budget outlays limitation.

Amends the Internal Revenue Code to limit the amount of interest that may be credited to such trust funds.

Amends Federal transportation law to require the Secretary of Transportation to estimate annually: (1) what, but for this Act, would be at the close of the next fiscal year the amount of unfunded aviation authorizations; and (2) the net aviation receipts at the close of such year.