What’s Changing 🔧
Japan’s National Tax Agency has announced that on September 24, 2026 the 国税システム (National Tax System, often called KSK2) will go live. Key updates will include:
- New formats for various 申告書 (tax return forms), 申請書 (applications), and 法定調書 (statutory reports) with updated field layouts and color schemes (most will now be black-and-white). (nta.go.jp)
- A shift from using fixed IP addresses for e-Tax system access to dynamic IP addressing—important for software vendors or institutional users who rely on IP filtering or trusted-host configurations. (nta.go.jp)
- Expansion of electronic notification (“処分通知等”) delivery options: the default consent method for e-notifications will change from case-by-case to advance single consent (事前の一括同意). (nta.go.jp)
- Display of submission date (提出年月日) directly on form headers in services that allow document retrieval. (nta.go.jp)
How This Affects Expats & Businesses
For Expats:
- If you left Japan and returned (or vice versa), ensure your tax obligations are up to date, as 年末調整 (year-end adjustment) and 確定申告 (tax return) rules will apply differently depending on your residency status. Forms may look different after September 24. (nta.go.jp)
- 扶養控除 (Dependent deductions) and related documents involving overseas family members may require updated or additional paperwork (translations, proof of relationship, etc.). These are already in effect for some categories since December 1. (nta.go.jp)
For Businesses / Software Providers:
- If you provide payroll or financial reporting services, your systems may need updating: new 法定資料 (statutory materials) submitted via optical disk or magnetic media will require compliance with updated data standards. Documents such as 源泉徴収票 (withholding slips) will see format changes. (nta.go.jp)
- The schedule for e-Tax specification documents (“仕様書”) is publicly posted, with the final version taking effect alongside the KSK2 roll-out. Ensure that your software is compliant by the key dates listed. (e-tax.nta.go.jp)
Practical Tips to Be Ready
-
Check your current software/vendor compatibility: If your payroll or filings software uses old formats, forms or conventions, schedule updates well before September.
-
Switch to e-Tax / My Number login methods: Since login flows and identifiers may change, adopting the マイナンバーカード方式 where possible can avoid issues. Note that the older ID & Password方式 will be discontinued starting from 令和9年分 (tax year 2027). (e-tax.nta.go.jp)
-
Review submission deadlines, especially for statutory reports like 源泉所得税支払報告書, 源泉徴収票, etc. After September 24, you must use the new formats. (nta.go.jp)
-
Maintain records of electronic‐notification consent: If you prefer to receive tax authority notices electronically, you’ll likely be required to provide advance blanket consent rather than per notification. (nta.go.jp)
-
Monitor maintenance windows: e-Tax will be unavailable during specific time periods around system migration. Plan submissions accordingly. (e-tax.nta.go.jp)
Example Scenario
Maria, a U.S. citizen working in Tokyo as a contractor, receives income from abroad and has a dependent living overseas. Under the new system:
- She must check whether her dependent qualifies for dependent deduction, and gather necessary documentation (translated, proof of relationship). (nta.go.jp)
- When submitting her year-end tax return after September 24, her withholding slips (源泉徴収票) will be in the new format, so she must ensure her employer or payroll service is compliant. (nta.go.jp)
- She decides to use My Number login to avoid issues with deprecated ID & Password login. (e-tax.nta.go.jp)
Bottom Line
The KSK2 system overhaul starting September 24, 2026 is a major milestone in Japan’s tax digitalization. Whether you’re an expat submitting your first Japanese tax return or a business managing payroll and filings, it’s essential to stay ahead: ensure updated forms, compliant systems, and timely submissions to avoid filing issues or penalties.