(かきとめ)

かきとめ
noun
registered mail
1. registered mail
A postal service that provides tracking and proof of delivery for important items.
Important documents should be sent by registered mail.
I signed for the package that arrived by registered mail.
I sent money by cash registered mail.

書留(かきとめ) is registered mail that provides tracking and requires signature upon delivery.

Types of registered mail in Japan:

Common expressions:

The name comes from the fact that the mail is 'recorded' (()()める = to write down/record).