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That Envelope in Your Mailbox: Telling Important Mail From Junk in Japan

✓ Last verified 2026-08-20 Sources: 7 sites 9 min read

The short version

Ask around and most foreign residents who have been in Japan more than a year have some version of the same story: a stack of unopened mail built up over a few weeks, assumed to be advertising, until one envelope turned out to be something that actually mattered. Matsudo City's own consumer warnings page exists partly because of how often people misjudge which letters need attention. This guide is not about reading Japanese. It's about the handful of physical signals — before you translate a single word — that tell you an envelope is worth opening carefully rather than setting aside.

Signal one: a sealed, pressure-glued postcard

A flat postcard that's been folded and pressure-sealed shut, rather than a normal open postcard you can read without opening, is called an atchaku hagaki (圧着ハガキ) in Japanese. Money Forward's guide to the residence tax decision notice (juuminzei kettei tsuchisho) describes this sealed-postcard format as one of the standard ways that notice gets delivered to salaried employees, and explains why: the notice carries personal income figures, so it's sealed rather than sent as an openly-readable card. Musashino City's own page on reading your individual residence tax payment notice documents the same pattern for its own mailings.

That's one specific, well-documented example, not a blanket rule for every important letter — plenty of other municipal and insurer mail arrives as an ordinary window envelope instead. But if a sealed postcard that needs to be pulled apart along a perforated edge shows up in your box, treat that format itself as a reason to open it rather than recycle it: something inside was considered sensitive enough to seal.

Signal two: it needed a signature, or was logged as delivered

Ordinary letter mail in Japan just gets dropped in your box. Two other services exist specifically so a sender can prove something was delivered, and municipalities and insurers reach for them when a notice is time-sensitive or a deadline is about to pass. Nagoya City's Consumer Affairs Center lays out the difference:

Either one landing in your box, or a delivery slip from Japan Post saying they tried to hand you a registered item while you were out, is worth treating as a strong signal. It means someone paid extra specifically so they'd have proof of when it reached you — which is not something anyone bothers with for advertising.

As with the sealed postcard, this isn't the only way important mail travels. A great deal of genuinely important notice — including from the same municipal offices — still goes out as a plain letter with no tracking of any kind. Use both signals as reasons to look closer, never as a filter for deciding something is safe to ignore because it lacked them.

Who tends to send mail like this

The senders that show up most often behind a sealed postcard or a signed-for envelope are your municipal (city or ward) office, the national health insurance section of that same office, the health insurance union tied to a former employer, and the Japan Pension Service. If you've recently changed jobs, left one without lining up the next, or are handling residence tax for the first time on your own rather than through payroll withholding, our guides to residence tax, health insurance after quitting a job, and the My Number card cover what those specific notices are generally about once you've established that an envelope is worth reading in the first place. This guide stops at "here's why this looks important" — it doesn't work out what any specific bill or notice means for your situation, since only your municipal office or insurer can do that from the actual document.

When you can't read what's inside

Two starting points work well together rather than as substitutes for each other. Minato City's living guide lists the consultation desks many municipalities now run, some staffed in a dozen or more languages and some backed by a tablet translation service for anything not covered by a bilingual staff member. Bring the letter itself rather than just describing what it says. For a faster first pass before you go anywhere, OCR-based translation apps that read text through your phone's camera are a practical option; LO-PAL's roundup of translation apps used by foreign residents in Japan is a reasonable starting point for comparing what's available.

Treat an app's translation as a rough first read rather than something to act on directly, especially for anything with a deadline, a payment amount, or legal language attached. A mistranslated word in a tax or insurance notice is exactly the kind of mistake worth avoiding, and that's what the in-person counter is for. If the letter mentions a due date and you genuinely can't get it translated before then, calling or visiting your municipal office directly, even without a translation in hand, beats letting the date pass unaddressed.

The scam version of this same envelope

The flip side of learning what real official mail looks like is recognizing an imitation of it. Matsudo City's own consumer-warning page documents fake "unpaid national health insurance premium" messages, sent by text and email rather than post in the cases it describes, that push recipients toward paying through a smartphone payment app link instead of the normal channel of a payment slip or a municipal-office counter. The tell isn't the formatting. It's the request. A real notice from your municipal office, insurer, or the pension service points you to a payment slip, a bank transfer, or an in-person or phone process through that same office. It will never ask for a reply text, a convenience-store payment code read out over the phone, or a gift card. If a message pushes you toward any of those, that request is the actual warning sign, independent of how official the rest of the message looks.

The reliable rule underneath both signals is the same: when in doubt, open it. A sealed postcard or a signed-for envelope raises the odds something matters, but plenty of ordinary-looking mail matters just as much. Sorting mail by how official the envelope looks, rather than opening anything that might be from a municipal office, insurer, or the pension service, is the habit that leads to a missed notice.

What this guide doesn't cover

This is about recognizing that an envelope deserves attention, not about what to do once you've read it. It doesn't work out how much you owe on a specific tax or insurance notice, doesn't interpret a specific legal notice for you, and doesn't cover business or delivery-service mail like a missed parcel slip — that's a separate everyday errand covered elsewhere on this site. For anything with a number attached that you need to act on, your municipal office or insurer's own counter is the right place to ask — a general guide like this one stops short of that.

This article describes general, commonly observed patterns in how Japanese municipal and insurer mail is formatted and delivered. It is not a complete or universal rule — practices vary by municipality and sender — and it is not tax, insurance, or legal advice. If you're unsure whether a specific letter is genuine or what it requires of you, contact your municipal office or the sender directly rather than relying on this guide alone. Content last verified against the sources below: 2026-08-20. See the disclaimer.

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Sources

All sources below were checked on 2026-08-20.

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