# What is Certified timestamp (認定タイムスタンプ)?

> A certified timestamp (認定タイムスタンプ) is a time-attestation issued by a time-stamping operator accredited by Japan's Minister for Internal Affairs and Communications. It evidences that electronic data existed at a given moment and has not been altered since, and it is required for scanner-based retention of national-tax documents under 電子帳簿保存法.

Last updated: 2026-08-07

- Japanese: 認定タイムスタンプ (にんていたいむすたんぷ / Nintei Taimu Sutanpu)
- In English: Certified timestamp (also rendered: accredited time-stamp, time-stamp token (TST))
- Governed by: Operators accredited by Japan's Minister for Internal Affairs and Communications (総務大臣).

Time-stamping in Japan moved from a private accreditation scheme run by the 日本データ通信協会 to a national one: in 2021 the 総務省 established rules for accrediting time-stamping operators (令和3年総務省告示第146号), making it a state accreditation. Accredited operators must, among other requirements, use digital-signature-based time stamps and reference the UTC(NICT) time source maintained by the National Institute of Information and Communications Technology.

For buyers, this matters in one specific way: when evaluating an expense-management or document-retention tool that claims 電子帳簿保存法 compliance, 'has timestamps' and 'uses a certified timestamp from an accredited operator' are different statements. Scanner-based retention of tax documents is where the distinction has teeth.

It is also worth separating a timestamp from a signature. A signature evidences who agreed; a timestamp evidences when the data existed and that it has not changed. Electronic contract services commonly apply both — the signature for attribution, the timestamp for integrity over the retention period, which for tax documents runs for years.

Rules and accredited-operator lists change. Confirm the current requirement against the 総務省 and 国税庁 material before relying on a vendor's compliance claim.

Sources: [1] https://www.soumu.go.jp/main_sosiki/joho_tsusin/scendou/time_business.html [2] https://www.nta.go.jp/law/joho-zeikaishaku/sonota/jirei/

## Related terms

- [Electronic Bookkeeping Act (電子帳簿保存法)](https://agent-door.com/glossary/denshi-chobo-hozon-ho)
- [Electronic Signature Act (Japan)](https://agent-door.com/glossary/denshi-shomei-ho)
- [Japan's Invoice System (インボイス制度)](https://agent-door.com/glossary/invoice-system)

## Frequently asked questions

### Is any timestamp acceptable for 電子帳簿保存法?

No. Scanner-based retention of national-tax documents requires a timestamp from an accredited time-stamping operator, not merely any recorded time. When a vendor advertises 電帳法対応, ask specifically which accredited operator it uses.

### Do we still need timestamps if the system has audit logs?

Audit logs are maintained by the same party that holds the data, so they evidence internal record-keeping rather than independent proof. A certified timestamp is issued by an accredited third party, which is why the retention rules reference it specifically. Some retention routes allow alternative measures — check the current 国税庁 guidance for your case.

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