"Asset Tax Navi" Releases "Aging Depreciation Checker" for Fixed Asset Tax – AI Determines if Depreciation in Valuation is Correctly Reflected Simply by Inputting Building Age and Structure

Fixed asset tax information service "Asset Tax Navi" (https://shisanzei.xyz) has released the "Aging Depreciation Checker," an AI tool that checks whether the aging depreciation of buildings is correctly reflected in their assessed value. Tool URL: https://shisanzei.xyz/tools/depreciation-checker

### Why Are Fixed Asset Tax Assessment Errors So Common?
Fixed asset tax is a system where municipalities calculate the assessed value of land and buildings and levy tax by multiplying that value by a tax rate (standard 1.4%). Taxpayers typically pay the amount on their tax notices as is, with few verifying the assessment calculation process themselves. However, a 2012 Ministry of Internal Affairs and Communications survey on fixed asset tax assessments revealed that 1,669 out of 1,721 municipalities nationwide (97.0%) experienced some form of assessment "correction" (Source: Ministry of Internal Affairs and Communications "Survey Results on the Status of Tax Amount Corrections for Fixed Asset Tax and City Planning Tax," 2012). The majority of corrections involved overestimation of assessed value (i.e., overcharging of tax).
Among the most common causes of assessment errors are "unreflected or incorrectly reflected aging depreciation." The fixed asset tax assessed value of a building is calculated by multiplying its reconstruction cost valuation points at the time of new construction by an aging depreciation adjustment rate. This aging depreciation adjustment rate is calculated based on standards set by the national government (Ministry of Internal Affairs and Communications) according to the building's structure (wood, steel frame, reinforced concrete, etc.) and its age. However, there are reported cases where the structural classification is incorrectly registered, extensions or renovations are not reflected, or the adjustment rate update is overlooked during the triennial reassessment. As a result, a certain number of property owners continue to pay higher taxes than necessary for many years.

### How the Aging Depreciation Checker Works
This tool allows taxpayers to easily check whether the aging depreciation is appropriately reflected in their building's assessed value.

**Information to Input:**
- Building structure (wood, light steel frame, heavy steel frame, reinforced concrete, steel-reinforced concrete)
- Construction year (year built)
- Total floor area
- "Assessed value" stated on the fixed asset tax statement (included with the tax notice sent annually from April to May)
- Location (prefecture, municipality)

If the structure and construction year are unknown, they are listed on the certificate of registered matters (Tofficial register). These can be obtained via the Legal Affairs Bureau's online service.

**Check Flow:**
1. **Calculation of Aging Depreciation Adjustment Rate**
The tool calculates the elapsed years from the input structure and construction year, and then computes the aging depreciation adjustment rate based on the supplementary table of the "Fixed Asset Valuation Standards" set by the Ministry of Internal Affairs and Communications. For example, for a 20-year-old wooden house, the adjustment rate would be approximately 0.26 (about 26% of the initial assessed value).
2. **Estimation of Theoretical Assessed Value**
For a building with the same structure and total floor area, a theoretical assessed value is estimated by referencing the average reconstruction cost valuation points in the region. Although this is an estimate, an alert is displayed if there is a significant discrepancy from the input assessed value.
3. **Determination of Deviation Rate**
The difference between the input assessed value and the theoretical estimated value is displayed as a "deviation rate" in percentage. If the deviation rate exceeds a certain level, the judgment result is displayed in three stages:

**Deviation Rate Less Than 10%: "Generally Appropriate"**
It is highly likely that aging depreciation is appropriately reflected. However, as this tool is a simplified check, utilizing the public inspection system (described later) is recommended for a rigorous verification.

**Deviation Rate 10-30%: "Confirmation Recommended"**
There may be some discrepancy in the reflection of aging depreciation. This could be due to incorrect structural classification registration, unreflected extensions/renovations, or unique regional adjustments. Please compare the details on your tax statement with the registered matters.

**Deviation Rate Over 30%: "Detailed Review Required"**
The assessed value significantly deviates from the theoretical value. This could be due to incorrect structural classification registration or failure to update the adjustment rate during reassessment. We strongly recommend inquiring with the municipal fixed asset tax department.

**4. Guidance on Next Actions**
Based on the check results, specific next actions are provided:
- How to check the tax statement and what items to look for
- How to use the public inspection system (annually from April 1st to April 20th or until the first payment deadline)
- Overview of the review request (formal procedure for appealing assessed value if dissatisfied)
- Cases where consulting a tax accountant specializing in fixed asset tax is effective

### Why Focus on "Aging Depreciation"?
The assessed value of fixed assets consists of "land" and