# 所得税法 / Income Tax Act — 第十八条 (Supplementary Provisions, Article 18) This is the Markdown twin of https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18. Every law, and how to address a provision: https://japanlaw.org/llms.txt. The same laws as MCP tools (no sign-in): https://japanlaw.org/mcp. - Law: 所得税法 (Income Tax Act), 昭和四十年法律第三十三号 - English title "Income Tax Act": Ministry of Justice translation - Kind: Act — the distinction between 法律 (Act), 政令 (Cabinet Order), 省令 (Ministerial Order) and 条例 (local ordinance) decides who may issue it and what it may say. - Provision: 第十八条 (Supplementary Provisions, Article 18)（純損失の繰戻しによる還付に関する経過規定） — address `suppl-3401-33/art-18` - Text in force since: 2026-10-01 - URL (the page that opens at this provision): https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18 - e-Gov law ID: 340AC0000000033 — never renamed. A permanent link, `/l/{lawId}/{address}` on this site, redirects to the page. - Every provision below carries its address and its URL on the line under it. - Japanese text: e-Gov 法令検索, Digital Agency (デジタル庁). English: as marked on each line below. Only the Japanese as published by the government has legal effect; the text below is a copy of it. Every English rendering below is a translation and says which kind: the Ministry of Justice's translation, or this site's machine translation, whose model and date the Sources list names. They are never merged and never substituted for one another. --- ### 第十八条（純損失の繰戻しによる還付に関する経過規定） — Transitional Provisions Concerning Refunds Based on Carryback of Net Loss caption: machine translation, not official suppl-3401-33/art-18 · https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18 **第一項** 新法第百四十条第一項（純損失の繰戻しによる還付の請求）（新法第百六十六条（非居住者に対する準用）において準用する場合を含む。）の規定は、昭和四十年以後の各年において生じた純損失の金額について適用し、昭和三十九年以前の各年において生じた純損失の金額については、なお従前の例による。 suppl-3401-33/art-18/par-1 · https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18/par-1 Article 140, paragraph (1) (Claim to Be Issued a Refund Based on Carryback of Net Loss) (including as applied mutatis mutandis pursuant to Article 166 (Application Mutatis Mutandis to Nonresidents) of the New Act) of the New Act applies to a Net Loss incurred in 1965 or any subsequent year, and the provisions then in force continue to govern a Net Loss incurred in 1964 or any prior year. machine translation, not official **第二項** 新法第百四十条第五項（新法第百六十六条において準用する場合を含む。以下この条において同じ。）の規定は、昭和四十年一月一日以後に同項に規定する事由が生じた場合について適用し、同日前に当該事由が生じた場合については、なお従前の例による。 suppl-3401-33/art-18/par-2 · https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18/par-2 Article 140, paragraph (5) of the New Act (including as applied mutatis mutandis pursuant to Article 166 of the New Act; the same applies hereinafter in this Article) applies where the circumstances prescribed in that paragraph arise on or after January 1, 1965, and the provisions then in force continue to govern where such circumstances arose before that date. machine translation, not official **第三項** 新法第百四十条第五項の規定を適用する場合において、同項に規定する純損失の金額のうちに旧法第三十六条（純損失の繰戻しによる還付）の規定による還付を受けるべき金額の計算の基礎となつた金額があるときは、当該金額を当該純損失の金額に相当する金額から控除した金額をもつて当該純損失の金額とみなす。 suppl-3401-33/art-18/par-3 · https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18/par-3 Where Article 140, paragraph (5) of the New Act is applied, if the Net Loss prescribed in that paragraph includes an amount that served as the basis for calculating the amount to be refunded pursuant to Article 36 (Refund Based on Carryback of Net Loss) of the Former Act, the amount obtained by deducting that amount from the amount equivalent to that Net Loss is deemed to be that Net Loss. machine translation, not official --- ## Cites - suppl-3401-33/art-18/par-1: 新法第百四十条第一項 → 所得税法 第百四十条第一項 (Article 140, paragraph (1)), art-140/par-1 — https://japanlaw.org/ja/income-tax-act/art-140/par-1 - suppl-3401-33/art-18/par-1: 新法第百六十六条 → 所得税法 第百六十六条 (Article 166), art-166 — https://japanlaw.org/ja/income-tax-act/art-166 - suppl-3401-33/art-18/par-2: 新法第百四十条第五項 → 所得税法 第百四十条第五項 (Article 140, paragraph (5)), art-140/par-5 — https://japanlaw.org/ja/income-tax-act/art-140/par-5 - suppl-3401-33/art-18/par-2: 新法第百六十六条 → 所得税法 第百六十六条 (Article 166), art-166 — https://japanlaw.org/ja/income-tax-act/art-166 - suppl-3401-33/art-18/par-2: この条 → 所得税法 附則第十八条 (Supplementary Provisions, Article 18), suppl-3401-33/art-18 — https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18 - suppl-3401-33/art-18/par-3: 新法第百四十条第五項 → 所得税法 第百四十条第五項 (Article 140, paragraph (5)), art-140/par-5 — https://japanlaw.org/ja/income-tax-act/art-140/par-5 ## Cited by 2 provisions cite this one. No official source publishes this direction. - 所得税法 附則第十八条第二項（純損失の繰戻しによる還付に関する経過規定） — https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-18/par-2 - 所得税法 附則第三十三条第一項（政令への委任） — https://japanlaw.org/ja/income-tax-act/suppl-3401-33/art-33/par-1 --- ## Sources - e-Gov 法令検索, Digital Agency (デジタル庁) — 所得税法 — the text in force from 2026-10-01 (https://laws.e-gov.go.jp/law/340AC0000000033/20261001_507AC0000000070), retrieved 2026-10-05 - Japanese Law Translation Database System, Ministry of Justice (法務省) — Income Tax Act — Ministry of Justice translation (https://www.japaneselawtranslation.go.jp/en/laws/view/3120/tb), retrieved 2026-09-18 - claude-opus-5[1m] — Machine translation, batch income-tax-act-20260918T180319-045, translated 2026-09-18 - This site's parser, version 225 — 所得税法 — structure, counts, cross-references and defined terms, computed 2026-10-05