Name the mismatch before judging it
A physical building can differ from its registry, building-confirmation record, approved plans, inspection certificate, tax record, or current use. Common examples include extensions, enclosed balconies, converted garages, additional rooms, removed walls, merged units, changed structure, floor-area differences, and unregistered ancillary buildings.
Do not jump from “unregistered” to either “illegal” or “harmless.” Registration, building approval, planning compliance, physical safety, and tax assessment are distinct systems. The buyer needs to identify what changed, when, by whom, under which approval, and what can now be corrected or demonstrated.
Build a five-record reconciliation
Compare: current land and building registry; building-confirmation and inspection records; approved plans and later applications; fixed-asset tax records; and measured physical condition. Use a marked plan showing every difference in area, outline, floor, structure, and use.
Collect seller disclosure, renovation contracts, invoices, drawings, photographs, warranties, insurance claims, and past sale or finance documents. Date the work as closely as possible because the rules and available procedures may differ.
Ask an architect or other qualified building professional to classify the physical and approval issue, a land and house investigator or judicial scrivener to address registration, and a tax professional or authority for tax consequences. Do not ask one adviser to conclude outside scope.
Missing inspection evidence is not the same as prohibited work
MLIT provides guidance for investigating existing buildings where an inspection certificate cannot be confirmed. The route can involve a current-status investigation by qualified professionals, but it does not recreate historical approval automatically or guarantee lender acceptance. Establish the exact deliverable and what it proves.
An old building may have incomplete records because of age or document retention. A newer extension may have been constructed without required procedure. They are different risk profiles. Record evidence rather than applying the same label.
Where a certificate or authority record exists, match it to the subject building. A document for the original house does not approve a later garage conversion or third floor.
Test planning and structural consequences
Recalculate building coverage, floor-area ratio, setbacks, height, fire, use, and other applicable controls including the added work. Determine whether the extension sits over a setback, boundary, easement, septic area, or utility route. Check structure, foundations, connections, waterproofing, drainage, ventilation, and fire separation.
Removing or altering structural elements can matter even when total floor area is unchanged. Enclosing a balcony or changing a garage to habitation can create load, moisture, fire, egress, light, ventilation, and parking issues. A visual renovation review is not enough.
For a condominium, determine whether work affected common property and whether association approval exists. Restoration may be required independently of public building compliance.
Quantify finance, insurance, and tax effects
Provide the mismatch file to the intended lender before the financing deadline. A lender can decline, value only registered area, require correction, shorten the term, or request professional evidence. Cash buyers should test the next buyer's likely route.
Ask the insurer to quote using actual area, structure, use, and known work. Incorrect property description can create coverage problems. Confirm whether corrective construction changes premium or acceptance.
Tax assessment can differ from registry. Determine whether past or future fixed-asset tax, acquisition tax, depreciation, or building-land allocation needs correction. Do not use unregistered area as “free space” outside ownership cost.
Choose the seller action before contract
Possible outcomes include seller registration correction, approval or current-status investigation, removal or restoration, delivery of specialist evidence, price change with buyer acceptance, a precise closing condition, or rejection. Select the outcome after understanding feasibility, cost, time, and residual uncertainty.
If the seller performs work, define scope, professional, approvals, inspection, registration, evidence, completion date, and remedy. A promise to “legalise later” is not a closing condition until the required result can be tested.
If the buyer accepts a mismatch, preserve the analysis and disclose it accurately in future finance, insurance, renovation, leasing, and sale.
Mismatch decision table
For every difference record: physical description; registry treatment; approval treatment; tax treatment; structural and use consequence; boundary or road consequence; correction route; cost and time; lender and insurer position; seller commitment; and residual resale risk.
The decision should state which facts are verified and which remain assumptions. A low purchase price is not a solution if the buyer cannot describe the asset accurately afterward.
Worked mismatch example
Assume the registry describes a two-storey, 110 m² wooden house, the tax record reflects 126 m², and the physical building contains an enclosed ground-floor garage and rear extension. The seller has renovation invoices but no building-confirmation or inspection record for the added work. The listing values the house using 126 m².
The buyer should commission measurement and architectural reconciliation, investigate authority records, identify structural and fire work, obtain the registry correction route, and ask the lender and insurer how they treat the 16 m² difference. If the extension occupies setback or exceeds current capacity, registration alone will not solve the planning issue. If it is compliant but unregistered, correction may still affect timing and tax.
Price should be based on the supported asset and corrective cost, not automatically on either 110 m² or 126 m². The example shows the workflow; it does not conclude legality from a mismatch pattern.
Questions each professional should answer
The architect or building reviewer should identify the physical change, structural and fire implications, applicable approval path, current conformity evidence, and feasible corrective work. The survey or registration professional should identify measured area, registered description, required application, supporting documents, and timing. The lender and insurer should state how the actual condition affects acceptance, valuation, cover, and required correction. The tax adviser or authority should address assessment and basis consequences.
Ask the seller to provide evidence and authority for corrective applications. Do not let several advisers each assume another has concluded legality. The buyer's issue register should show the exact boundary between scopes and the remaining gap.
If correction is a closing condition, name the accepted final document rather than stating only that the seller will “handle registration.”
Primary sources
- MLIT — Guidance where an existing building lacks an inspection certificate: https://www.mlit.go.jp/jutakukentiku/jutakukentiku_house_fr_000061.html
- MLIT — Existing-building use and renovation guidance: https://www.mlit.go.jp/jutakukentiku/content/001967456.pdf
- MLIT — Existing-home inspection guideline: https://www.mlit.go.jp/seisakutokatsu/hyouka/content/001338301.pdf
- MLIT — Outline of real-property registration: https://www.mlit.go.jp/common/001050449.pdf
- RETIO — Roads and site-condition disputes: https://www.retio.or.jp/dispute_search_category/dispute1-1/
Reviewed against the linked sources on 23 August 2026. The actual authority, registry, building, lender, insurer, and tax conclusions control.
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