FROM CBP: U.S. Customs and Border Protection (CBP) will allow you to enter the U.S. with up to five liters of alcohol duty-free as part of your exemption - as long as at least four liters were purchased in the insular possession, and at least one of them is a product of that insular possession. Additional bottles will be subject to a flat duty rate of 1.5% and subject to Internal Revenue Service taxes.