noun
revenue stamp
A stamp affixed to documents to pay government fees or taxes, similar to a fiscal stamp.
契約書に収入印紙を貼る必要がある。
You need to affix a revenue stamp to the contract.
切手 is a postage stamp for mailing, while 収入印紙 is a revenue stamp for paying government fees.
Compound of 収入 (revenue) and 印紙 (stamp). The term directly describes its function as a stamp for revenue collection.