Whether you go through customs at London Gatwick depends on where your journey started and what you are carrying. If you are arriving on an international flight from outside the UK, you will pass through customs after you have cleared passport control and collected your checked luggage. Gatwick, like most UK airports, uses a "channel" system: the Green Channel is for those with nothing to declare (meaning they are within their duty-free allowances), while the Red Channel is for those who need to declare goods, commercial items, or currency over £10,000. If you are a domestic passenger flying within the UK, you generally do not have to clear customs upon arrival. For passengers in transit who are "checked through" to another international destination and stay within the sterile airside zone, customs is usually avoided. However, if your bags are not checked through or you choose to exit the airport during a layover, you must clear immigration and customs. Even in the Green Channel, Border Force officers perform spot checks to ensure compliance with laws regarding prohibited items like certain foods, plants, or excess alcohol.