総務省｜信書便事業｜信書のガイドライン

This page presents the Ministry of Internal Affairs and Communications guidelines on 'Shinsho' (letters/documents). Shinsho is defined as "documents expressing the sender's intention or notifying facts to a specific recipient" under postal laws. Examples include letters, invoices, receipts, applications, contracts, invitations, permits, and certificates. Documents not considered Shinsho include books, newspapers, catalogs, checks, prepaid cards, tickets, and credit cards. The guidelines provide detailed criteria to distinguish between Shinsho and non-Shinsho documents, supporting accurate judgment in letter delivery business operations.