The short version
- A naitei tsuchisho (offer letter) isn't just a friendly heads-up. Japanese case law has long treated accepting one as forming an actual employment contract, so an employer can't withdraw it as casually as a verbal promise.
- Seishain, keiyaku shain, and haken are three different legal relationships, not just three prestige tiers: who technically employs you, and how easily that relationship can end, differs between them.
- Whatever your contract says, it legally can't set conditions worse than the Labor Standards Act. Any clause that tries is simply void, and the Act's baseline fills the gap automatically.
- Shiyou kikan (the trial period) gives an employer more room to end things in your first 14 days specifically. After that, dismissal still needs grounds a court would recognize as reasonable, even during probation.
- Renew a fixed-term contract past a combined five years with the same employer and you gain the right to apply for indefinite-term status, under Article 18 of the Labor Contract Act.
A one-page PDF lands in your inbox with a company seal in the corner and a line congratulating you on joining. Underneath it sits a short list of Japanese terms your translation app only half handles: seishain, shiyou kikan, kishoku. None of it feels like the start of a binding legal relationship. In Japan, depending on what you do next, it already might be.
What a naitei tsuchisho actually is
Naitei tsuchisho (内定通知書) is the written notice of an informal job offer, usually sent after interviews and before a start date is reached. It is easy to read as a courtesy letter, something short of a real commitment on either side. Japanese courts have not generally treated it that way. A widely cited 1979 Supreme Court ruling (Petty Bench, July 20, 1979, Minshu Vol. 33 No. 5 p. 582, commonly known as the Dai-Nippon Printing case after the printing company that was the defendant) held that accepting a naitei generally forms an employment contract starting on the agreed date. That contract is subject only to specific conditions the employer reserved in advance — legal commentators describe it as a contract "with a reserved right of cancellation," not an open option for the employer to simply change its mind.
The practical upshot: an employer withdrawing a naitei after you have accepted it is not something they can generally do for any reason they like. Courts have applied something close to the same reasonable-grounds standard used for dismissing an existing employee. This guide isn't the place to judge whether a specific withdrawal was lawful — that turns on facts a court would need to weigh. If it happens to you, the general labor consultation corner covered later in this guide is the place to ask, not a forum thread.
Three ways to be hired, and why the label matters
Japanese job listings and offer letters lean on a handful of employment-type labels that describe a real legal difference, not just a status tier. The three you will most often see on a foreign resident's offer:
| Seishain (正社員) | Keiyaku shain (契約社員) | Haken shain (派遣社員) | |
|---|---|---|---|
| Who employs you | The company you work at, directly | The company you work at, directly | A staffing agency; you're placed at a separate client company |
| Contract term | No fixed end date (muki koyou) | Fixed term (yuki koyou), commonly renewed yearly | Fixed term, set by the agency-client dispatch agreement |
| Ending it mid-term | Needs grounds a court sees as objectively reasonable (Labor Contract Act Art. 16) | Needs "unavoidable circumstances" — a stricter bar than Art. 16 (Labor Contract Act Art. 17) | Governed by the dispatch agreement between agency and client; the client can end the placement more easily than it could fire a direct hire |
| A rule specific to this type | Broadest general dismissal protection of the three | Five-year rule can convert the contract to indefinite term (below) | Capped at 3 years in the same client-company unit under the Worker Dispatch Act |
Haken is the one that trips people up most, because the company you physically report to on a given morning is not the company holding your employment contract. Your pay, your enrollment in social insurance, and any dismissal all run through the staffing agency, not the client business — worth confirming directly with the agency if your offer describes the role this way.
The floor under every contract: the Labor Standards Act
Whatever your specific contract, or your employer's internal rules of employment (shugyo kisoku 就業規則), happen to say, none of it can legally set worse conditions than the Labor Standards Act (労働基準法) provides. Any clause that tries — say, an unpaid trial month, or a contract that waives overtime pay entirely — is void on that point, and the Act's own standard fills the gap automatically. That principle runs in both directions through the system: a company's shugyo kisoku itself is void wherever it undercuts the Labor Standards Act, and an individual employment contract is likewise void wherever it undercuts the shugyo kisoku or the Act. Employers with 10 or more employees are legally required to draft shugyo kisoku, file them with the local Labor Standards Inspection Office, and make them available to staff — so if you have never seen your company's copy, you are entitled to ask for it.
Separately, at the point a contract is concluded or renewed, the employer must clearly notify you in writing (email or a company portal counts, if you agree to that format) of a specific set of items: contract length, workplace and duties, working hours and holidays, wages, and retirement provisions, among others required under the Act's implementing ordinance. This written-notice rule was updated effective April 2024 to require some additional detail, including the scope of possible future changes to your workplace or duties. If your written notice is missing entirely or looks thinner than this list, that's worth raising with HR before you sign, not after.
Shiyou kikan: what the trial period does and doesn't allow
Most Japanese offers include a shiyou kikan (試用期間), a probationary period typically running one to six months, three months being the most common length reported across employer guides. During it, the employer is generally understood to have somewhat broader discretion to decide you aren't a fit, reflecting the period's purpose: actually observing your work rather than judging you on paper alone.
One specific rule sits inside this period. Under Article 21 of the Labor Standards Act, an employer can end your employment within your first 14 continuously employed days without the 30-day advance notice (or pay in lieu of notice) that dismissal ordinarily requires. Past that 14-day mark, the standard notice rule applies again, probation or not.
Notice period is not the same question as whether a dismissal is valid at all. Even inside probation, and even past the 14-day mark, courts have continued to apply the same abuse-of-right framework from Article 16 of the Labor Contract Act — objectively reasonable grounds, judged as appropriate under general social standards — while generally giving employers somewhat more latitude during this evaluation window than they'd get dismissing a confirmed employee. Vague or discriminatory reasons don't automatically clear that bar just because you're still on probation.
Fixed-term vs. indefinite: the five-year rule
A keiyaku shain contract on a one-year renewal cycle can look, in practice, indistinguishable from permanent employment after enough renewals. Japanese law gives that situation a specific mechanism. Under Article 18 of the Labor Contract Act — introduced in a 2012 amendment and generally applicable to fixed-term contracts starting from April 2013 — once your combined fixed-term contracts with the same employer exceed five years, you gain the right to apply for conversion to an indefinite-term contract (muki tenkan 無期転換). If you apply, the employer is deemed to accept; there's no discretion on their end to refuse it. Your working conditions after conversion generally carry over as they stood on your last fixed-term contract, unless a different agreement is reached, so conversion changes the contract's term, not automatically your pay or duties.
A handful of exceptions and special categories exist, including certain highly skilled professionals and continuing-employment arrangements for retirees. Some employers have also restructured renewal practices specifically to stop short of the five-year mark, a pattern sometimes called "muki tenkan nogare." Whether that restructuring is lawful in a specific case is exactly the kind of question this guide won't try to answer for you. It depends on the facts of your renewal history, and it's a fair question to bring to the consultation window below.
A short glossary
| Kanji | Romaji | English |
|---|---|---|
| 内定通知書 | naitei tsuchisho | written offer notice |
| 雇用契約書 | koyou keiyakusho | employment contract |
| 正社員 | seishain | permanent, directly hired employee |
| 契約社員 | keiyaku shain | fixed-term, directly hired employee |
| 派遣社員 | haken shain | dispatch/agency employee |
| 試用期間 | shiyou kikan | probation/trial period |
| 有期雇用 / 無期雇用 | yuki koyou / muki koyou | fixed-term / indefinite-term employment |
| 無期転換 | muki tenkan | conversion to indefinite-term status |
| 就業規則 | shugyo kisoku | company rules of employment |
If something about your offer or contract feels wrong
This guide explains how the system is generally structured. It cannot tell you whether your specific naitei withdrawal, your specific probation dismissal, or your specific contract clause holds up, because that always depends on facts a general article isn't written with. Two public, free channels exist for exactly that situation:
- Your regional Labour Standards Inspection Office (労働基準監督署), which enforces the Labor Standards Act itself — the right first stop for a written-notice failure, unpaid wages, or an unlawfully short notice period.
- The General Labor Consultation Corner (総合労働相談コーナー), staffed at prefectural labour bureaus, which covers a broader range of workplace disputes including contract and dismissal questions, and offers foreign-language consultation — including English — on set days at many locations. It's free, and an interpreter can generally be arranged if you don't speak Japanese.
Neither office is a lawyer, and neither replaces one for a contested case, but both are built for exactly the kind of "is this normal" question a new hire in Japan tends to have.
What comes after you sign
Once your contract starts, the paperwork doesn't stop — it just changes shape. Your first payslip is where the abstractions in this guide turn into actual numbers: our line-by-line guide to reading a Japanese payslip (kyuyo meisai) covers the earnings and deduction sections you'll see from week one. And if the employment relationship this guide describes ends someday, whether that's a keiyaku shain contract running out or a seishain role you leave voluntarily, our guide to health insurance after you quit your job in Japan covers the enrollment choices that follow.
Sources
Checked 2026-08-15. This environment's direct page-fetching tool returned access-blocked errors for the government and law-firm domains below, so the summaries above draw on search-engine result snippets rather than a full read of every page — described here plainly rather than overstated.
For the official English translations of the underlying statutes, including Articles 13, 15, 16, 17, 18, and 21 referenced above, see the Japanese government's Japanese Law Translation portal: Labor Standards Act (japaneselawtranslation.go.jp) and Labor Contracts Act (japaneselawtranslation.go.jp). For the Worker Dispatch Act's 3-year assignment cap, see the Act on Securing the Proper Operation of Worker Dispatching Businesses (japaneselawtranslation.go.jp) and Fukuoka Now's plain-language explainer for foreign residents (fukuoka-now.com). For the 1979 Supreme Court ruling on naitei as contract formation, see The Japan Times (japantimes.co.jp) and the Japan Institute for Labour Policy and Training's background paper on the Labor Contract Act's enactment (jil.go.jp). For the Article 18 five-year conversion rule, see JILPT's summary of the 2012 amendment (jil.go.jp). For the Article 17 "unavoidable circumstances" standard for mid-contract dismissal of fixed-term employees and the void-if-below hierarchy between contracts, shugyo kisoku, and the Labor Standards Act, see Monolith Law Office (monolith.law). For shugyo kisoku filing requirements at companies with 10 or more employees, see Global Advisory Experts (globaladvisoryexperts.com). For the April 2024 update to the written working-conditions notice requirement, see GOAL-sr's HR-practice summary (note.com). For probation-period length norms and the Article 21 fourteen-day notice exclusion, see Lexology's Japan termination overview (lexology.com). For the General Labor Consultation Corner and multilingual Foreign Workers Consultation Corner network, see the Ministry of Health, Labour and Welfare's guide (mhlw.go.jp). Statutes, thresholds, and enforcement practice can change; confirm current rules with your Labour Standards Inspection Office or the General Labor Consultation Corner before relying on anything above.