Lying on a customs form—also known as making a "false declaration"—is a serious offense in 2026 that carries severe legal and financial penalties. If a U.S. Customs and Border Protection (CBP) officer finds that you willfully misrepresented items (such as not declaring high-value jewelry, commercial goods, or more than $10,000 in cash), the items can be immediately seized and forfeited to the government. Financially, you can be hit with civil penalties that often range from the domestic value of the item up to several thousand dollars per violation. Furthermore, lying on a federal form can lead to the permanent revocation of Global Entry or TSA PreCheck status, making future travel significantly more difficult. In extreme cases involving the smuggling of prohibited items or large sums of undeclared currency, you can face criminal prosecution, resulting in heavy fines and potential imprisonment. For non-citizens, a finding of "willful misrepresentation" can even lead to being found inadmissible to the United States, potentially barring you from entry for the rest of your life.