The core rule for customs is total transparency: you must declare everything you are bringing into a country that you didn't have when you left. In 2026, major rules for entering the U.S. include declaring any currency over $10,000, all food (especially fruit, meat, and seeds), and commercial goods intended for resale. Most travelers have a "duty-free" allowance, often up to $800, but any purchases exceeding this must be reported and may be taxed. You should keep your receipts organized and ensure that any prescription medications are in their original packaging with your name on them. Prohibited items generally include illegal drugs, certain plants that could carry pests, and counterfeit "knock-off" luxury goods. If you are unsure about an item, the best practice is to declare it to avoid fines or seizure of the goods.