← Back to AI Legal Lab
Insight
Legal Outsourcing

Certified-Content Mail: Legal Effects and When to Use It, Before You Send

Hello, I'm Noriaki Asato, Representative Attorney at LegalAgent.

Before sending certified-content mail (naiyo shomei yubin) in the belief that "once we send it, the other side will be forced to pay or respond," check what effect it actually has. Certified-content mail itself has no power to seize the other party's assets or to legally compel them to act. What Japan Post certifies is limited to the objective facts of when a document was sent, by whom, to whom, and with what content. Whether the claim stated in the document is correct under substantive law, and whether the other party is obliged to comply, are separate matters.

What Certified-Content Mail Certifies and the Rules for Preparing It

Certified-content mail is a system under which Japan Post certifies the date of sending, the sender, the addressee and the text of the document, by means of a copy prepared by the sender. It must be sent as general registered mail; it cannot be handled as simplified registered mail. What is certified is the existence of the document and the fact that it was sent; the truth or legal validity of the assertions stated in it is not certified. With this character in mind, consider adding express delivery or certificate of delivery. Adding a certificate of delivery gives you material proving the fact and date of delivery, but it does not officially certify the identity of the person who actually received it.

The copy submitted to the post office is subject to limits on the number of characters and lines. For vertical writing, the limit is 20 characters per line and 26 lines per page. For horizontal writing, the text must fit one of the following formats: 20 characters per line and 26 lines per page; 13 characters per line and 40 lines per page; or 26 characters per line and 20 lines per page. These character and line limits are rules applying to the copy, and the content document actually delivered to the other party is not subject to similar format restrictions. Any paper and writing instruments may be used, and there is no problem with preparing it on ordinary copy paper. The addresses and names of the sender and addressee are added at the end of the copy, but this may be omitted if the content document already contains the same information.

When Sending It Is Appropriate and When It Backfires

Certified-content mail works effectively in practice in situations where you should clearly preserve, as evidence, the fact that a notice was sent and its wording. Typical examples include demanding payment, with a deadline, from a counterparty who is in arrears on a sales price or outsourcing fee; demanding repayment of a loan; communicating a declaration of intent to terminate a contract; and requesting that infringement of a copyright or trademark right cease. If the other party later disputes the matter, saying "we never received such a demand" or "the termination notice never arrived," Japan Post's records allow you to show objectively the fact of sending and the content of the document.

In the case of a termination notice in particular, because arrival of the declaration of intent is a requirement for it to take legal effect (Article 97 of the Civil Code), whether and when it arrived tends to become an important point of dispute. By using a certificate of delivery as well, you can secure evidence objectively showing the date on which the notice reached the other party's sphere of control. Note, however, that arrival of a declaration of intent is judged legally in light of the individual circumstances, so it is not the case that every refusal to accept delivery is automatically deemed arrival.

On the other hand, there are situations in which sending certified-content mail works against you in negotiations. If you suddenly send certified-content mail at a stage where there is still room for an amicable resolution through voluntary discussion and you want the business relationship to continue, the other party may harden its position and refuse to talk. Because certified-content mail may be taken as a strong warning, misjudging the timing could turn a matter that could have been resolved through discussion into an all-out confrontation.

In addition, if you send it while the claim contains factual errors or legal mistakes, it will remain as unfavorable evidence in later litigation or other proceedings. Even if you send a correction, the wording you sent may be scrutinized for consistency with the original statements. Before delivery, it may be possible to retrieve the mail, but check the conditions and fees. Separately, because Article 540, Paragraph 2 of the Civil Code does not permit withdrawal of a declaration of intent to terminate, avoid sending a termination notice on the assumption that you can unilaterally undo it after the contract has been validly terminated. Before sending, it is important to check that there are no errors in the provisions on which the claim is based or in the calculation of amounts.

Cautions on Suspension of Completion of Prescription by Demand

One important use of certified-content mail is suspension of the completion of extinctive prescription by a demand under Article 150 of the Civil Code. This is a mechanism under which, where the extinctive prescription period for accounts receivable or a similar claim is about to expire but preparations to file a lawsuit immediately cannot be completed in time, the completion of prescription is suspended for six months from the time the demand reaches the other party.

There are two points to keep in mind in practice. First, suspension of completion by demand is merely a temporary way of buying time. It is not a system that adds six months to the original expiry date of the prescription period, so during the six months of suspension you must take legal action such as a judicial claim, a demand for payment procedure or compulsory execution, or obtain an acknowledgment of the debt from the other party to renew the prescription period. If the original prescription period has also expired and there is no other ground for suspension of completion or renewal, prescription is completed six months after the demand. Provisional attachment is a separate ground for suspension of completion, but it does not by itself give rise to the effect of renewal, under which the prescription period starts running again from the beginning. Second, under Article 150, Paragraph 2 of the Civil Code, even if a further demand is made during the suspension period, that repeated demand is not given the effect of suspending completion. You cannot keep postponing the completion of prescription by sending demand letters over and over again.

Ordinary mail and email can also constitute a demand under the Civil Code. Certified-content mail and certificates of delivery are used as means of being able to show later the content of the demand and the date of arrival. In matters involving prescription, it is appropriate to proceed with preparations based on when the original prescription period expires and which procedure should be chosen within six months after arrival.

Choosing in Whose Name to Send It and Points to Check Before Sending

Certified-content mail can be sent in the company's own name, but sending it in an attorney's name has its own practical significance. An attorney sending a notice as the company's representative clearly shows the other party that the company has settled on a course of action with legal proceedings in view, and it can also prompt the other party to consider consulting their own representative. In addition, because the legal basis for the claim and the calculation of amounts are organized before sending, deficiencies in the wording are less likely to arise.

If you send a letter in the company's name and then send another in an attorney's name, any inconsistency in the assertions or change in calculations between the two documents may be pressed by the other party, with the risk that the credibility of your position as a whole is undermined. In complex disputes or cases where the other party is likely to retain a representative, it is worth considering from the outset whether to send the letter in an attorney's name.

Another option for certified-content mail is electronic certified-content mail (e-naiyo shomei), which can be sent via the internet. Under this system, you upload an electronic document prepared in Word format to a dedicated system, and Japan Post prints the document, verifies and encloses it, and delivers it to the other party as registered mail. It is not a service that sends an email to the other party. More characters can be written per page than on a copy submitted at the counter, applications are accepted 24 hours a day as a rule, saving you the trouble of going to a post office, and costs may be lower when sending the same text to multiple addressees. Note, however, that the service may be suspended for scheduled maintenance and similar reasons, and that the legal status of the document itself is the same as for ordinary dispatch at the counter.

Before sending certified-content mail, make a final check that supporting evidence such as contracts and delivery notes is in place, that there are no errors in the amount claimed or the facts constituting grounds for termination, and how you want to continue or end the relationship with the other party. By having an expert check the content before sending, together with Initial Response When a Business Partner's Breach of Contract Is Suspected and Reviewing Termination Clauses, you can reduce the risk of the content of the claim or the validity of termination being disputed later. LegalAgent provides ongoing support, from reviewing the wording of certified-content mail to everyday contract work, as Legal Outsourcing, and we handle matters after negotiations break down through our Litigation and Dispute Resolution team.

Related articles

Articles connected to this topic.

Insight / 2026.10.04 How a Company Should Respond to a Request for Collective Bargaining: Community Unions, the Duty to Bargain in Good Faith and Collective Agreements Insight / 2026.10.04 Tax Audits and Appeals Against Reassessments: Deadlines for Requests for Reinvestigation, Requests for Reconsideration and Tax Litigation Insight / 2026.10.03 Internal Use and Copyright: What to Check When Sharing Articles, Preparing Training Materials, and Using AI Summaries

Services connected to this topic

Legal outsourcing Ongoing legal team support for contract review and legal operations.
View AI Legal Lab articles