National Tax Agency Discusses Next-Generation System "KSK2" and Tax Investigations on Cryptocurrency Assets

The National Tax Agency began full-scale operation of its next-generation system "KSK2" on September 24, 2026, marking the first major update in about 25 years. The previously separate databases for different tax categories have been integrated, allowing for cross-referencing of multiple tax categories for the same taxpayer.

The National Tax Agency states that by centralizing the information it holds across tax categories, it will be able to execute tax administration more fairly and appropriately.

What position will cryptocurrency assets, which can span multiple tax categories, hold in this update? The CoinPost editorial team conducted a written interview with the National Tax Agency regarding the background of the update, the significance of cross-category data referencing, and the realities of investigations into cryptocurrency transactions. The responses are published as the National Tax Agency's views.

Constraints of Paper-Based Administrative Operations

The next-generation system, which is being fully operational for the first time in about 25 years, has been launched. It is said that the current system has long been designed based on paper forms, but what was the biggest constraint in terms of administrative operations?

The system was based on the initial design of administrative operations, such as outputting entered content for confirmation on forms.

Although some data digitization has progressed due to the promotion of electronic filing, there were restrictions on the information that could be incorporated into the existing KSK system.

As a result, the operations were based on paper, making the administration cumbersome and the usability poor for various data analyses.

Editorial Note: KSK stands for "National Tax Comprehensive Management (KOKUZEI SOUGOU KANRI)" and is the core system of the National Tax Agency that connects national tax offices and tax offices via a dedicated network to centrally manage declaration and tax payment information. Trial implementation began in January 1995, and nationwide implementation was completed in November 2001. It is also used for selecting investigation targets and managing delinquent payments, and the current KSK2 is its successor.

Significance of Cross-Category Data Referencing

The concept of the update is the integration of tax category-specific databases. Cryptocurrency assets are subject to income tax on capital gains, while also being subject to asset tax in cases of gifts and inheritance, making them assets that can span multiple tax categories.

The integration of tax category-specific databases is a key concept of the update. While cryptocurrency assets can span multiple tax categories, what significance do you think cross-category data referencing will have for the administration?

The previous KSK system built separate systems and databases for each administrative category, such as taxation and debt management, resulting in insufficient cross-category data referencing.

In KSK2, the databases are integrated, and great care is taken in setting reference permissions, allowing for the centralized management and search of multiple tax categories from income tax to asset tax for the same taxpayer.

National tax offices believe that centralizing the information they hold across tax categories will enable them to execute tax administration more fairly and appropriately.

Discrepancy in Additional Tax Amounts per Case

In the fiscal year 2024, the additional tax amount per case for investigations of individuals engaged in cryptocurrency transactions was 7.45 million yen, which is 2.5 times the overall additional tax amount of 2.99 million yen for income tax field investigations. How do you analyze the factors contributing to this discrepancy?

The National Tax Agency is making efforts to collect and analyze various materials and information that are tax-effective, including submitted tax returns, and conducts tax investigations when issues are recognized, including for those who have not filed declarations. They are also working to understand the transaction realities related to new economic transactions involving cryptocurrency.

While a detailed analysis of why the additional tax amount per case is high compared to the overall income tax field investigations has not been conducted, it is believed that the significant price fluctuations in cryptocurrency transactions and the potential for large profit amounts depending on the transaction scale are contributing factors.

Editorial Note: The National Tax Agency's investigations are divided into "field investigations," where staff physically visit, and "simple contacts" to correct declaration contents via documents, phone calls, or requests to visit the office. Field investigations are further divided into deeper "special investigations and general investigations" and shorter "focus investigations." The comparison benchmark of 2.99 million yen is the average additional tax amount per case for 36,404 special and general investigations conducted in fiscal year 2024, while the 7.45 million yen for cryptocurrency transactions is the average for 613 cases in the same category.

The additional tax amount for cryptocurrency transactions exceeds the overall average (fiscal year 2024).

Positioning Compared to Other Income Areas

How do the number and scale of undeclared cases related to cryptocurrency transactions compare to other income areas?

In fiscal year 2024, the additional undeclared income amount and additional tax amount per case for investigations related to cryptocurrency transactions are relatively high, but comprehensive comparisons with other income areas have not been conducted, making it difficult to provide a definitive positioning.

In any case, the National Tax Agency aims to ensure that those who properly declare and pay taxes do not feel unfairness, and will continue to strive for appropriate and fair taxation through various initiatives, including tax investigations.

Scope of Material Information Collection

As a starting point for investigations, "material information" may include online postings, social media posts, and online service usage histories. What do these specifically refer to?

As for the targets of material information collection, social media posts and online service usage histories may be included. What specifically do these refer to?

Regarding your question about the targets of material information collection, it pertains to the discovery of tax evasion cases and is related to investigation methods. Therefore, we refrain from answering from the perspective of preventing tax crimes.