To amend the Internal Revenue Code of 1986 to modify the application of the tonnage tax on vessels operating in the dual United States domestic and foreign trades, and for other purposes.

Amends the Internal Revenue Code to modify the alternative tax on qualifying shipping activities to treat a corporation electing such tax as continuing to use a qualifying vessel in the U.S. foreign trade during any period of use in the U.S. domestic trade, thus eliminating the 30 day limitation on operating in U.S. domestic trade under current law.