This bill, known as the "Sporting Goods Excise Tax Modernization Act," amends the Internal Revenue Code of 1986 to redefine the responsibility for collecting excise taxes on certain imported sporting goods. It specifically designates certain marketplace providers as the importers for tax purposes, shifting this obligation from the original manufacturer or seller. This change primarily targets online platforms that facilitate the sale of goods transported into the United States from abroad. A marketplace provider is defined as any entity that both hosts or facilitates product listings and collects and transmits gross receipts from the purchaser to the seller. The new rule applies to "specified marketplace sales" where an article is imported into the U.S. in connection with a sale, and the manufacturer is not the marketplace provider. An exception is made if the tax would otherwise be imposed on a person other than the purchaser. The amendment will take effect for sales occurring in calendar quarters beginning 60 days after the bill's enactment.