Sending Affidavit / Statutory Declaration from Thailand to Japan — Complete 2026 Handbook
Last reviewed: 2026-06-18 · By NAATI Thailand Editorial Team · English edition
Japan is one of the most paperwork-intensive destinations for a Thai affidavit because Japanese authorities still expect a fully certified chain even after Thailand deposited its instrument of accession to the Hague Apostille Convention on 30 June 2026, with entry into force for Thailand on 28 February 2027. Whether the affidavit is being used for marriage registration at a Shiyakusho, for the family court (Katei Saibansho) in adoption or custody matters, or for a visa case before the Immigration Services Agency, the document must arrive with an Apostille, a sworn Japanese translation (公文書翻訳), and a koseki-friendly transliteration of every name. This guide explains the production standards NAATI Thailand uses so the receiving office accepts the file the first time.
Legal basis in Japan
Japanese authorities recognise foreign affidavits under Article 118 of the Code of Civil Procedure and Article 27 of the Hōrei (now the Act on General Rules for Application of Laws). For family-law filings the Family Registration Act (Koseki Hō) governs the form requirements: marriages, divorces, and recognitions of paternity all require originals plus certified Japanese translations. Thailand deposited its accession to the 1961 Hague Apostille Convention on 30 Jun 2026, effective 28 Feb 2027; once in force the Thai Apostille is expected to replace the Japanese embassy legalisation step, but until then documents need Thai MFA legalisation plus the embassy step the receiving office requires. Translators are not formally licensed in Japan, but most municipal offices and family courts insist on translations produced by an agency registered with the Japan Translation Federation (JTF) or by a Gyoseishoshi-lawyer who can stamp the translation.
Receiving authorities and acceptance rules
Three classes of receiving authority dominate Japanese-bound affidavits. (1) Shiyakusho / Kuyakusho (municipal offices) handle marriage and birth registrations and require the affidavit to mirror the names in the koseki tohon exactly, including katakana for Thai names. (2) Family Courts handle adoption, custody, and inheritance affidavits and require the Apostille and the translator's seal to be visible on the same page. (3) The Immigration Services Agency handles spouse-visa and long-term-resident affidavits and additionally requires the affiant's residence card number when the affiant is in Japan. Every Japanese office demands originals; PDFs or photocopies are refused as a matter of policy.
End-to-end workflow handled by NAATI Thailand
Day 0: we draft the affidavit in English with parallel Japanese, lock the katakana transliteration of the affiant's name against the passport's MRZ field, and confirm the receiving office's preferred kanji for any place names. Day 1: you sign before a Thai notarial-services attorney with passport in hand; the attorney executes the jurat in English. Days 2–4: MFA Apostille (standard 3 days, express 1 day). Days 5–7: certified Japanese translation by a JTF-registered translator including a stamped declaration of accuracy. Days 8–10: courier delivery to the Shiyakusho, Family Court, or Immigration office of record.
Common pitfalls and how we screen for them
Common rejection reasons: (1) Katakana mismatches against the koseki — the municipal office will refuse the marriage filing on the spot. (2) Use of the affiant's nickname instead of the full legal name printed in the passport. (3) Translations produced in Thailand that omit the JTF stamp; some Family Courts will accept only translations carrying a domestic translator's seal. (4) Affidavits drafted in the first person that omit the formal jurat language; Japanese offices look for the explicit oath clause. (5) Apostilles printed double-sided in a way that obscures the affiant's signature on photocopy.
Cost and turnaround
Itemised cost (June 2026): Thai notary fee quoted after document review; MFA Apostille at the official government fee (THB 400 normal / THB 800 express per stamp); JTF translation price on request; EMS or DHL Express price on request. Total price on request. Timing depends on document type and the receiving authority; staff estimate after reviewing the documents — not a guarantee. We can ship directly to the Shiyakusho or to a Gyoseishoshi-lawyer who will hand-deliver on your behalf.
Anonymised case studies
Marriage registration at Shibuya Ward Office
Illustrative scenario: A Thai bride needed a Single-Status Affidavit accepted by Shibuya-ku. We aligned the katakana to her residence-card spelling and produced the JTF-stamped translation; acceptance remained the ward office's decision.
Adoption affidavit at Yokohama Family Court
Illustrative scenario: An adopting Thai parent submitted an affidavit consenting to a special adoption (tokubetsu yōshi engumi). We drafted the jurat against Family Registration Act art. 17 and supplied a translator's certificate on JTF letterhead; accepted without supplementary filings.
Spouse-visa renewal in Osaka
Illustrative scenario: An Immigration Bureau caseworker requested an affidavit confirming continued cohabitation. Illustrative scenario: the document set covered legalisation and translation; timing depended on the authorities and is not a guarantee.
In-depth FAQ
Editorial conclusion
A Japanese-bound affidavit is a name-discipline exercise as much as a legal exercise: passport, koseki, residence card, and katakana must all align before the document is signed. NAATI Thailand does that name reconciliation up front and ships a JTF-stamped translation with the Apostille to reduce the risk of the Shiyakusho, Family Court, or Immigration officer returning the file.
