noun
customs declaration form
Official form used to declare goods when entering a country.
税関告知書に持ち込み品を記入してください。
Please fill in the items you are bringing on the customs declaration form.
税関申告書 is a more common term for customs declaration form; 税関告知書 is a specific official name used in some contexts.
Compound of 税関 (customs) + 告知 (notification) + 書 (document).