This is the 2577th most frequent Japanese word.
届け出
Notification; report; filing; registration.
届け出 refers to the act of filing a formal notification with an authority in this context.
住民票の変更には市役所への届け出が必要です。
To change your resident card, filing a notification at the city hall is required.
届け出 is used to denote the required reporting to the authorities about incidents here.
事故が起きた場合、まず警察への届け出を行ってください。
In case of an accident, first, please make a report to the police.
届け出 indicates informing or notifying others formally in this instance.