Sometimes an authority will assess completed work through a retrospective permit, regularization application, certificate, or other local route. There is no single North American or UK process, and the terms do not mean the same thing everywhere. A route may be unavailable for a particular unit, may address only one approval layer, or may require substantial investigation and corrective work. Filing an application does not itself make a unit approved or safe to occupy.

Find the route for the correct authority

First identify the location, the unit type, how it was created, when the work occurred, and whether the issue is planning or zoning, building control, fire, trades, or another approval. These are often separate decisions. If an authority has issued a notice, order, or enforcement deadline, address that process directly rather than assuming a regularization application pauses it.

Published examples show how different the routes can be:

  • In England and Wales, GOV.UK describes building-regulations regularisation for certain completed work done without consent, through a local-authority building-control body. It says this route covers work carried out after 11 November 1985 and that alterations may be needed before a certificate is issued. The page explicitly notes separate rules in Scotland and Northern Ireland.
  • In California, state law provides a framework, but the City of San Diego’s bulletin shows how one municipality applies a local process to qualifying pre-2020 ADUs and junior ADUs. The city’s submittal, site-condition, fee, and inspection requirements remain specific to San Diego.
  • Berkeley’s pilot program offers two different local outcomes for qualifying unpermitted ADUs and JADUs: a building-permit route with zoning review and a Certificate of Occupancy, or a Housing Certificate of Compliance route focused on Housing Code and minimum fire and life-safety standards. The City’s comparison identifies different permit, fee, and continuing-compliance conditions for the two routes. See the Berkeley pathway guide; its requirements do not apply to other California cities.
  • Edmonton says its secondary-suite permit application includes suites that already exist without permits. Required development, building, or trade permits and inspections still have to be completed; an application is not a final status finding.
  • Vancouver describes an optional inspection service for an existing secondary suite, followed by plans, applicable permits, required work, trade permits, and inspections. The City says the suite is not considered legal until the final inspection passes.
  • Calgary’s process has distinct planning, building, registry, inspection, and construction-date considerations; see the Calgary legalization guide.
  • In New York City, DOB says its response to an illegal conversion begins by determining whether the work can be legalized or must be removed. Where a route is available, its guidance lists approved plans and permits, licensed corrective work, final DOB sign-off, a new Certificate of Occupancy, and a separate Certificate of Correction. The NYC correction guide explains that local sequence; it does not establish eligibility or an outcome for a particular property.
  • Certain existing occupied NYC basement and cellar apartments have a separate Local Law 126 temporary-residence pilot. DOB’s current ADU program page says it is not accepting Authorization for Temporary Residence applications. This route is distinct from the general correction sequence above; check DOB’s current guidance for its status and limits.

These examples illustrate questions to ask; none supplies a route for another city or a determination for a particular property.

Prepare for investigation and correction

Authorities may ask for proof of the construction or conversion date, permit history, existing plans, measured drawings, a site plan, current-use details, photographs, professional reports, or access for inspection. If finished walls conceal electrical, plumbing, structural, or fire-separation work, the authority may require opening the work so it can be inspected. The scope and cost depend on the property and local process; do not assume a prior owner completed the required checks.

A reviewer may identify corrections, require current permits for later alterations, or direct the owner to remove work that cannot be approved. Safety, fire, access, utility, environmental, zoning, and title issues can involve different authorities. A retrospective process does not erase those separate checks.

Understand what completion means

Keep each outcome distinct: an application received, a planning decision, a building permit, a passed inspection, a regularization certificate, a completion record, and permission for a stated use are not interchangeable. Ask the issuing authority what document closes the process and exactly which work, dwelling, date, and conditions it covers. Then compare that scope with the unit as it exists today. See completion certificates and legal-status records.

If no clear route is published, ask the responsible planning or building office for a written, property-specific answer. A qualified designer or contractor may help prepare plans, but only the relevant authority can decide the application and required approvals.