Civil Litigation
Certified Content Mail (내용증명)
Reviewed 2026-08
In short
- Certified content mail (내용증명) is a postal service: the post office certifies what you sent and when, and keeps a copy for 3 years. It is evidence, not an order — it forces nothing by itself.
- Its legal work is real but specific: it proves notices were given, fixes dates, and — as a formal demand — can provisionally interrupt the statute of limitations.
- That interruption survives only if you escalate within 6 months — lawsuit, payment order, or attachment (Civil Act art. 174). A letter with no follow-up preserves nothing.
- Anyone can send one from any post office or online, no lawyer required— and foreign-language letters are accepted.
- Your letter is evidence against you too: write facts and a clear demand, not threats and admissions.
Sooner or later, most disputes in Korea produce the same advice from every Korean friend and colleague: “send a naeyong jeungmyeongfirst.” A deposit that isn’t coming back, an invoice nobody answers, a contract the other side quietly stopped performing — the standard opening move is a formal letter through the post office, not a phone call and not yet a lawsuit.
Certified content mail (내용증명)is a certification service of the postal system, run under the Postal Service Act’s implementing rules (우편법 시행규칙): you bring three identical copies of a letter, and the post office certifies their content and the sending date — one copy to the recipient, one back to you, one kept at the post office. Nothing about it involves a court.
What matters is knowing exactly what this letter does and does not accomplish — because both overestimating it and skipping it are expensive. This guide covers its actual legal effects, when to send one and when not to, how to write it, and the 6-month rule that decides whether it protected your claim at all.
1. What it is — and what it is not
The mechanics are simple. The post office compares your three copies, stamps each with the sending date and a certification that this exact text was mailed, sends one to the other side, and archives one for 3 years — during which either the sender or the recipient can request re-certification or inspection of the archived copy. The result is tamper-proof evidence of content + date + parties.
What it is not: a court document, an enforcement instrument, or an obligation on the recipient to reply. Ignoring one carries no penalty by itself. Its force comes from what it sets up — the record it creates for the negotiation, the lawsuit, or the litigation that may follow. Think of it as the first page of a future court file, written while everyone is still being polite.
2. What it actually does, legally
| Effect | How it works | Basis |
|---|---|---|
| Proof of content and date | The certified text and sending date are beyond dispute later — no more “I never said that” / “you never asked.” | Postal certification (우편법 시행규칙) |
| Making notices effective | Many legal acts — terminating a contract, refusing a lease renewal, setting a cure deadline — take effect when the notice reaches the other side. Certified mail plus delivery certification proves both the notice and its arrival. | Civil Act art. 111 (arrival principle) |
| Pausing the limitations clock | A formal demand (choego) (최고) provisionally interrupts prescription — but only holds if followed by lawsuit, attachment, or similar within 6 months. | Civil Act art. 174 |
| Negotiation pressure | Not a legal effect, but the practical one: it signals that you know the process and are prepared to use it. Many disputes settle at this step. | — |
The third row deserves emphasis because it is the one people get wrong. If your claim is approaching its limitation period — 3 years for wages, for instance, or 10 for ordinary contract claims — the letter buys you a conditional 6 months, not a reset. Section 6 covers what has to happen inside that window.
3. When to send one — and when not to
Send onewhen a dispute needs a formal record: demanding payment of a debt or deposit, giving a lease notice that must be provable, terminating a contract for breach, setting a final deadline before you escalate, or answering an unfounded demand against you in a form that will read well in court. In the deposit context, the letter’s specific role in the recovery sequence is covered in Getting Your Housing Deposit Back.
Think twice in two situations. First, when speed matters more than paper: if the deadline is days away, file — a lawsuit or payment order interrupts prescription in its own right, and the letter can wait. Second, when warning the other side is itself the risk: a debtor who receives a formal demand has weeks of notice to move assets before you can attach them. Where asset flight is realistic, the usual sequence inverts — secure first, demand second. That call is worth professional advice before, not after.
4. How to write one
There is no prescribed form. A letter that works has five parts, in order: who you are and who the recipient is (names, addresses); the facts, with dates and amounts, stated neutrally; what you demand, precisely (“return ₩20,000,000 to the account below”); a deadline (commonly around two weeks); and what follows if it passes (“I will pursue legal proceedings without further notice”). One page is usually enough. Attach nothing you cannot afford to show a judge later.
Facts, dates, amounts, one demand, one deadline. The letter is written for two readers: the recipient today, and a judge later.
On language: the rules accept letters written legibly in Korean, Chinese characters, or other foreign languages — so an English letter can be certified. Practically, a Korean text (or a bilingual one) is usually the better tool: the recipient, their lawyer, and any court will work in Korean, and you want nothing lost or disputed in translation.
Your letter is evidence against you too
5. Sending it — post office, online, and proof of delivery
Prepare three identical copies
Signed, dated, with both addresses. At the counter, the post office verifies the copies match and stamps the certification on each.Or send it online
The e-certified mail service on the Internet post office (인터넷우체국) accepts letters around the clock, prints and delivers them, and archives the text electronically for the same 3 years.Add delivery certification (배달증명)
A small add-on that documents the date the letter was delivered — the piece you need when a notice takes effect on arrival. Add it at sending, and keep the confirmation.Keep your certified copy and every receipt
Your copy, the mailing receipt, and the delivery confirmation are the evidence set. If the envelope comes back refused or unclaimed, keep it sealed — the fact of refusal is itself worth proving.
If the letter cannot be delivered — the recipient moved, or refuses the mail — do not treat that as failure. The attempt is documented, refusal can be shown, and the next steps (address inquiries through court proceedings, service by other means) belong to the litigation stage, where the court’s own service machinery takes over.
6. After you send: the 6-month rule
A demand letter opens a window, and the window closes. If the letter served as your formal demand (최고) to preserve a claim near its limitation period, the interruption holds only if, within 6 months, you follow with a lawsuit, participation in bankruptcy proceedings, a summons for settlement, or a provisional attachment or injunction (Civil Act art. 174). Miss the window and the clock behaves as if the letter never existed.
So decide the follow-up before you send. The usual escalation paths — the payment order for undisputed money claims, the small-claims track up to ₩30 million, the ordinary lawsuit — each have their own economics, and which fits depends on the amount and whether the other side will fight. If the letter produces a reply and a negotiation, put any deal in writing with dates and amounts; if it produces silence, treat the silence as an answer and move within your window.
7. Common mistakes
- Treating the letter as the remedy. It is the overture, not the performance. A recipient who ignores it faces nothing until you escalate — so a letter without a follow-up plan is a bluff on paper.
- Missing the 6-month follow-up and losing the limitations protection the letter was sent to create.
- Writing in anger. Threats, insults, and criminal accusations create risks for you and value for the other side. If you cannot write it coldly today, write it tomorrow.
- Vague demands.“Resolve this matter promptly” proves you complained; it does not prove what you demanded. Name the amount, the account, the date.
- Sending to a stale address.Check the recipient’s current address first — a contract, a business registry extract, the property register. A perfectly drafted letter to an old apartment proves very little.
Deadlines
- 6 monthsAfter a demand letter that interrupts prescription — file a lawsuit, payment order, or attachment within this window, or the interruption evaporates (Civil Act art. 174).
- Your deadline in the letterCommonly around two weeks. Diary it — the credibility of every later step depends on you doing what the letter said you would.
- 3 yearsHow long the post office keeps the certified copy; either party can request re-certification or inspection in that period.
Before sending, know two dates: when your claim’s limitation period ends, and what you will do the day after your letter’s deadline passes.
Frequently asked questions
I received a 내용증명. Have I been sued?
No — it is a private letter, not a court document, and no deadline in it is set by law. But do not toss it: it usually signals a lawsuit being prepared, and your response (or silence) will be evidence later. Read it carefully, check what is actually true, and answer deliberately — in provable form — rather than by an angry phone call. If a court document does arrive later, the clocks change completely.
Can I send one in English?
Yes — the postal rules accept legibly written foreign-language letters, so an English letter can be certified and sent. Whether it should be is a different question: the recipient and any later court operate in Korean, so a Korean or bilingual version usually does the persuading. If the letter matters, have the Korean text prepared or checked by someone who drafts them.
The recipient ignored my letter. Now what?
Exactly what the letter promised. Silence past your deadline is your cue to escalate — payment order, small claims, or lawsuit, depending on the amount and the dispute. The letter has already done its work: the demand, the date, and the ignored deadline are now on the record for the court that comes next.
Does sending one stop my claim from expiring?
Only conditionally. As a formal demand it interrupts prescription provisionally, but the interruption survives only if you follow up within 6 months with a lawsuit, attachment, or similar step (Civil Act art. 174). Repeating letters does not extend this — the follow-up must be one of the listed proceedings, not another envelope.
Do I need a lawyer to send one?
No — individuals send certified content mail themselves every day, at the counter or online, and for a straightforward demand that is often enough. Letters sent under an attorney’s name are also common in practice, typically where the dispute is likely to escalate and the drafting — what to demand, what to concede, what not to write — starts to matter as much as the sending.
Written by Attorney Chulho Choi (SOL & LUNA / Law Firm Myeong, KBA-registered specialist in Civil and Criminal Law). Reviewed as of August 2026. Updated when laws change.
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