noun
demand note; dunning letter
A formal written notice demanding payment of an overdue debt, often sent by a creditor or collection agency.
督促状が届いたら、すぐに支払いを済ませたほうがいい。
If you receive a demand note, you should pay it right away.
Compound of 督促 (dunning, urging payment) and 状 (letter, document).