Customs; the government office or place that inspects imports/exports and collects duties, typically at airports or ports.
海外から戻るときは税関で申告する必要がある。
When returning from abroad you need to declare items at customs.
空港の税関で荷物を開けられた。
My luggage was opened by customs at the airport.
輸入品は税関の検査を受ける。
Imported goods undergo inspection by customs.