No document should be treated as a universal “ADU legal” certificate. Its meaning depends on the issuing authority, the approval route, the project date, and the precise use and work described. A useful status check asks: what did this authority approve or inspect, at which address, on what date, and does the current unit still match that scope?

Identify the document’s job

Possible records include a planning or zoning decision, building permit, approved plans, inspection sign-off, completion certificate, occupancy permit, regularization certificate, registry entry, property-information report, or an authority’s approved-use letter. These documents can answer different questions. A planning-law certificate may address whether a use or development is lawful under planning rules, while building control separately assesses technical requirements. An application receipt shows that a process began; it does not show that it passed.

Official examples make these differences concrete:

  • GOV.UK describes a regularisation certificate as a possible result after a local-authority building-control body assesses certain completed work and any required alterations.
  • In England, a lawful development certificate concerns lawfulness under planning legislation; it does not replace Building Regulations or other required consents.
  • Edmonton distinguishes an Occupancy Permit for new-home construction from the green sticker used after a successful final inspection for certain improvements to existing homes, including secondary suites.
  • Toronto’s Property Information Report describes permits on file, inspection status, and certain outstanding orders, but the City says it does not outline permitted use.
  • Berkeley’s pilot compares a Certificate of Occupancy with a Housing Certificate of Compliance. The City describes different permit, zoning-review, code, and continuing-compliance scopes; see the Berkeley pathway guide before treating either certificate as a general status label.
  • In New York City, a Certificate of Occupancy (CO) states legal use or permitted occupancy type. Depending on the building and work, the City also identifies a Temporary Certificate of Occupancy or a Letter of No Objection for certain pre-1938 buildings. The applicable record and scope must still be confirmed. The separate NYC illegal-conversion guide explains DOB’s correction and enforcement sequence.

Check identity, scope, and later changes

For every record, match the municipal address, parcel or building identifier, issuer, issue date, project description, unit count, approved use, plans, conditions, inspection status, and any open orders. Compare this with later alterations and the unit’s current layout and use. A permit for an earlier structure or a different scope does not necessarily cover the present dwelling.

Records may also leave out other approval layers. A zoning record does not establish fire or building-code compliance; a building inspection may not establish utility capacity, rental permission, title status, or private lender requirements. Request the relevant records from each responsible authority and ask what document closes that authority’s part of the process.

If the record is missing or unclear

Ask the local authority how to request a historic search of record or property report, and what identifiers and fees apply. If records conflict with the physical unit, ask whether a site inspection, approved-use letter, revised permit, or retrospective application is appropriate. Do not treat tax records, a real-estate listing, a photograph, or documents filed by an owner as equivalent to an authority’s approval or inspection result.

For a property-specific records workflow, see how to check an existing ADU and the Toronto Property Information Report guide. A final certificate proves only the scope stated by its issuer; confirm current status with that authority.