If Japan Post delivers someone else’s mail to you, its official instruction is to attach a note identifying the misdelivery and put the item into a Japan Post postbox, or report it to a nearby post office or customer service. Check the delivery company first: that procedure is not for items delivered by another carrier. Japan Post: mail addressed to someone else
Keep the envelope unopened while identifying the problem. This guide is based on Japan Post’s written instructions, not a tested return or a report about a particular delivery.
Check the recipient, address and carrier separately
The fact that an envelope is in your mailbox does not establish that it is yours. Equally, an unfamiliar sender does not establish that it was misdelivered.
Use this short comparison before choosing a return route:
| What you see | What to establish next |
|---|---|
| Someone else's name and a different apartment number | Whether it is a Japan Post item delivered to the wrong mailbox |
| Your address but a name you do not recognise | Whether it is for someone in your household, a previous resident, or another intended recipient; do not guess a forwarding address |
| Your name and address, but an unfamiliar sender | This is not enough to classify the item as someone else's mail |
| Another delivery company's service mark | Use that company's route for a delivery problem |
These are editorial examples for sorting the problem. Read the outside of the item; you do not need to open the contents to compare the name, address and delivery markings.
Japan Post specifically excludes items that it did not deliver from its misdelivery-return procedure. Letter-shaped packaging alone does not identify the carrier. If you cannot tell who delivered it, contact the company named on the label or ask the post office to help identify it before depositing it in a postal box. Carrier restriction in Japan Post’s FAQ
For unopened Japan Post mail, identify the misdelivery on a note
Once you have established that the item was delivered to you in error, attach a note to the outside. Do not cover the address or other information needed to identify the item.
An example note for this guide is:
誤配達です。
“This was delivered to the wrong recipient/address.”
That wording is an editorial example, not a required official form. Japan Post asks for a note stating that it was misdelivered; its FAQ offers the postbox route or contacting the post office/customer service.
Suppose, hypothetically, you live in apartment 301 and receive a Japan Post letter addressed to an unrelated person in 401. The useful information is that the delivered location and address do not match. You do not need to investigate the recipient, copy their personal details into a public forum, or work out a new mailing address yourself.
If the problem keeps recurring, or the address matches your home but the intended recipient is unclear, use the contact route. Describe what is written on the item and where it arrived, without inventing a reason for the mistake.
If you accidentally opened it, the instructions are different
Japan Post has a separate FAQ for this situation. It says to repair the mail item and attach a note stating that you opened it by mistake, including your name and address. Then use the indicated postbox route or contact the local delivery office/customer service. For another carrier’s item, contact that carrier instead. Japan Post: accidentally opened someone else’s mail
A note structure you can adapt is:
誤って開封しました。
氏名：［あなたの氏名］
住所：［あなたの住所］
The brackets are fields for your own details, not the intended recipient’s. This is a writing aid based on the official requirements, not a form submitted during this research.
Keep the contents with the envelope. Do not treat an already-opened item as though the unopened procedure fully describes your situation. If you are unsure how to repair it or supply the information, explain the accidental opening when you contact the delivery office.
Make the handback match the problem
Before handing it back, confirm three things: it belongs to someone else, you have identified the delivery operator, and the note matches whether the envelope was opened.
This procedure concerns correcting a misdelivery. It does not decide a shopping return, a refund, unwanted goods addressed to you, or another person’s mail-forwarding application. Those questions require a different process.
No delivery correction time is promised here. If you contact Japan Post about repeated or unusual deliveries, retain the reply or reference it provides and follow the instructions for your actual item.