On 2026-09-25, KDDI and Okinawa Cellular issued an official announcement to prevent SMS phishing and impersonation fraud. The companies will implement the shared SMS number mechanism jointly introduced by Japan’s four major mobile carriers, while also advancing the migration of service notifications to RCS.
1. SMS sender ID transition: On 2026-10-06, the sender ID for au PAY two-factor authentication SMS will be switched to the unified public number `00055000`; from October 14, au ID two-factor authentication SMS will also be sent using the same number. Other official SMS messages from KDDI will subsequently be gradually consolidated under public numbers in the `0005` range. No manual action is required from users.
2. RCS migration roadmap: By the end of fiscal year 2027, KDDI plans to migrate all official user-facing notifications to officially verified RCS business account channels. Official RCS notifications have already been prioritized for RCS users since May 2026. RCS supports images and videos and is gradually rolling out end-to-end encryption. As of August 2026, KDDI’s RCS user base had surpassed 21 million.
This framework was jointly established by the four carriers—KDDI, NTT docomo, SoftBank, and Rakuten Mobile. Dedicated sender numbers beginning with 0005 are assigned only to enterprises that have passed the carriers’ qualification reviews, enabling users to quickly identify official messages. The numbers also support inbound replies. Japan’s Ministry of Internal Affairs and Communications Working Group on Preventing Improper Use has positioned this mechanism as a core anti-fraud measure to improve the trustworthiness of A2P SMS, and credit card companies, insurers, securities firms, law firms, and other institutions have already adopted it.
Japan continues to tighten controls over A2P SMS sender IDs. For enterprise OTP and transactional notifications, carrier-approved `0005` public short codes should be used as a priority, while regular mobile numbers used as A2P sender IDs are being progressively restricted. At the same time, regulators are encouraging transactional services to upgrade from SMS to RCS.
