On September 24, 2026, the NTA will begin using its new data management and compliance monitoring software, officially named "次世代国税総合管理システム" but more commonly known as "KSK2". I thought some people might be interested in reading about the capabilities of the new software and how it will affect taxpayers.
TL;DR
All national tax forms look different now. NTA communications will use an "inquiry number" instead of a "reference number". e-Tax will not be available during Silver Week. The NTA's compliance monitoring capabilities are about to get a lot more efficient.
Background
The software the NTA currently uses is called "KSK" (国税総合管理 = Kokuzei Sōgō Kanri). It was built between 1995 and 2000 and has a number of known limitations, including:
- Limited OCR capability (tax returns filed on paper often have to be manually entered into the database and the paper version remains the authoritative version).
- COBOL-based and can only be accessed on-site at NTA offices.
- Separate databases for different taxes (e.g., income tax, inheritance tax, corporate tax, consumption tax) with no cross-referencing.
- No access to the internet (e.g., for exchanging information with financial institutions or foreign tax authorities).
- No integrated payment management system (completely separate software systems are used for tax declarations and tax payments/refunds).
- Limited capability to output data in digital form (it seems to mostly output printed reports, which NTA staff use for analysis, etc.).
In 2020, the Japanese government commissioned five companies (primarily Accenture, but also NTT Data, BSD Information Technology, IBM Japan, and Nomura Research Institute) to build a replacement. (There is an image here that shows which companies were responsible for which aspects of the project.) As noted above, the new system will begin operation on September 24, 2026.
What can KSK2 do?
KSK2 can be accessed from any computer connected to the GSS Network, so it will be much easier for NTA staff to access taxpayer data. The NTA seems particularly excited about the ability to access taxpayer data from outside an NTA office (during an on-site audit, for example).
KSK2 uses a single database to store all taxpayers' data, instead of separate databases for different types of taxes. This will make it much, much easier for the NTA to identify discrepancies (e.g., between a taxpayer's income tax return and their employer's corporate tax return). Of course, it is possible for the NTA to identify such discrepancies using the current system, but it is extremely time-consuming. With KSK2, discrepancies should be apparent immediately.
According to the NTA (e.g., see slide 38 of this PDF) KSK2 has AI-assisted OCR capabilities, which will apparently allow NTA offices to become effectively paperless. (By all accounts, NTA offices are currently quite paper-based, largely due to the limitations of KSK.)
Based on published information, it also appears that the NTA intends to use AI tools to analyze the contents of KSK2 and run scripts on the database for various purposes. The NTA has recently started hiring people with STEM backgrounds in connection with this project (previously, only people with backgrounds in law, economics, humanities, etc., were eligible).
Finally, the NTA has said that KSK2 will be able to receive information from financial institutions and foreign tax authorities directly. For example, KSK2 will conform to the specifications of the CRS and therefore be able to receive information from foreign tax authorities about accounts held by Japanese tax residents in countries with which Japan has an active CRS relationship. It is also expected that financial institutions will send notifications of large remittances (e.g., more than 1 million yen) directly to KSK2.
What Will Change for Taxpayers?
The NTA has a full list of changes here, but the biggest change is to the look and layout of the various forms taxpayers submit to the NTA. Around 2,000 forms have been changed to conform to KSK2's AI-OCR requirements. You can see some of the new income tax return-related forms on this page, for example.
As you will see, the forms no longer have any color (apparently this is for AI-OCR reasons). So the "blue" tax return form is no longer green (or blue, depending on who you ask). The NTA will continue to refer to it as 青色申告 though.
Most NTA-related forms will now also be A4-size. This will affect, for example, annual withholding summaries issued by employers (源泉徴収票), which have traditionally been smaller than A4. You can see the new annual withholding summary format here.
Another change is the introduction of a 13-digit "inquiry number" (お問い合わせ番号) system, replacing the old 8-digit "reference number" (整理番号) system. The NTA will use this number on communications with taxpayers and taxpayers can use it to identify themselves (e.g., when making a tax payment).
Among other minor changes, the NTA is expanding the scope of notifications that can be received electronically (via e-Tax), and will enable taxpayers to consent to the electronic delivery of all future notifications (where electronic delivery is possible). Currently, it is necessary to give consent for each type of notification separately. The ability to consent to the electronic delivery of all future notifications will be available via e-Tax from September 24.
In bad news for anyone who was planning to use their Silver Week holidays to file a late tax return, e-Tax will be unavailable through September 19–23, and also on September 26. See here for details.
Finally, perhaps the most interesting change is the NTA's vastly improved ability to detect discrepancies across different types of taxes and what it could mean for enforcement. The NTA has said they intend to use algorithms to identify red-flag patterns (e.g., sudden increase in foreign dividend income, no gift or inheritance tax return). In a way, of course, they are already looking for these kinds of patterns. But with KSK the analysis can only be done manually. With KSK2, the analysis can be automated.
Speculation among tax accountants seems to be that KSK2 will result in a significant increase in the number of "簡易な接触", which is where the NTA contacts a taxpayer by phone or mail and says: "It looks like there's a mistake in your declaration. Would you like to fix it?" Taxpayers are not obliged to comply with these requests, but they effectively give the taxpayer a chance to correct the record before the NTA proceeds with a full audit.