"Souzoku AI" Launches Real Estate "Roadside Land Price vs. Market Value" Divergence Checker: AI Instantly Calculates the Gap Between Inheritance Tax Valuation and Market Price via Address Input

On April 14, 2026, Mycat Inc. (Headquarters: Meguro-ku, Tokyo) released the "Roadside Land Price vs. Market Value Divergence Checker" on its AI inheritance tax simulation service, "Souzoku AI" (https://souzoku-ai.xyz). This tool instantly calculates the divergence rate between a property's inheritance tax valuation (based on roadside land prices) and its actual market transaction price.

Tool URL: https://souzoku-ai.xyz/tools/land-gap-checker

Background: The "Invisible Loss" Caused by the Gap Between Roadside Prices and Market Values

Roadside land prices, published annually by the National Tax Agency in July, serve as the basis for calculating inheritance and gift taxes. While these are generally set at approximately 80% of the official land prices, significant gaps often emerge between these figures and actual real estate transaction prices (market values) depending on the region and location.

According to National Tax Agency statistics, land accounts for approximately 33.0% of inherited assets (Source: National Tax Agency, "Overview of Inheritance Tax Filing Results for 2022"). Despite real estate being a core component of inherited assets, discrepancies between valuation and reality can lead directly to overpayment or underpayment of inheritance tax.

In popular urban areas, market prices often significantly exceed roadside prices. Conversely, in regions facing population decline, roadside prices may exceed market values, resulting in an inheritance tax valuation that exceeds the property's actual worth. Many bereaved families face situations where they realize too late that "the tax is higher than expected" or "the land cannot be sold for enough to cover the tax."

Tool Features: Visualize the Divergence Rate by Simply Entering an Address

The "Roadside Land Price vs. Market Value Divergence Checker" uses AI to calculate and display the following information simply by entering the property address:

Input Items

• Property address (Prefecture to house number)
• Land area (in square meters, as listed on the real estate registry or fixed asset tax notice)
• Land category (Residential, farmland, forest, etc.; can be estimated as "residential" if unknown)

AI-Generated Analysis Results

1. Roadside Price-Based Valuation
Calculates the basic valuation by multiplying the roadside price of the road fronting the property by the land area. It also displays the adjusted valuation, accounting for major coefficients such as depth price correction and irregular shape correction.

2. Estimated Market Value Range
Refers to the latest transaction data from the Ministry of Land, Infrastructure, Transport and Tourism's "Real Estate Transaction Price Information" to estimate the market value range (upper to lower limits) based on local transaction history. In areas with limited data, it complements the estimate using official land prices and displays the estimation accuracy.

3. Divergence Rate and Impact Simulation
Calculates the difference between the roadside valuation and the estimated market value as a percentage. It also provides a rough simulation of how this divergence affects inheritance tax, considering the basic deduction (30 million yen + 6 million yen × number of statutory heirs).

4. Area-Specific Divergence Trend Map
Displays the divergence trends between roadside prices and market values in the surrounding area using a color-coded map, allowing users to visually grasp how divergence rates vary by distance from stations or zoning, even within the same municipality.

Intended Use Cases

1. Understanding Inheritance Estimates While Parents Are Healthy
Inheritance planning is often postponed, but knowing property valuations in advance expands options for lifetime gifting and tax payment preparation. April and May, when fixed asset tax notices arrive, are ideal times to confirm land areas.

2. Considering Inheritance Division Strategies
Deciding whether to "sell the land and divide the cash" or "have someone inherit the land" requires knowledge of both the roadside price (affecting tax) and the market price (affecting sales proceeds). This tool serves as a starting point for fair division among heirs.

3. Organizing Points Before Consulting a Tax Accountant
By providing experts with information such as "the gap between our land's roadside price and market value is this much," users can engage in more concrete discussions regarding topics like the applicability of large-scale land evaluations or special exceptions for small-scale residential land.

Development Roadmap

Future updates will include a portfolio feature to analyze multiple properties at once. For those holding multiple plots, comparing divergence rates will provide strategic decision-making material for determining which properties to gift during one's lifetime or which to use for payment in kind. We will also strengthen integration with existing "Souzoku AI" tools (such as the 3-second inheritance tax diagnosis and tax simulator) to create a seamless environment from property valuation analysis to total inheritance tax estimation.

Service Overview

• Service Name: Souzoku AI
• URL: https://souzoku-ai.xyz
• Roadside Land Price vs. Market Value Divergence Checker: https://souzoku-ai.xyz/tools/land-gap-checker
• Operator: Mycat Inc. (2-7-22 Mita, Meguro-ku, Tokyo)
• Corporate Website: https://mycat.business