First identify the authority that approved the system
Do not begin with a generic records request to every nearby office. Use the province's regulatory model and the property's location to identify the likely custodian. If the property has changed municipal boundaries or the system is old, the current office may need to tell you where historic files were transferred.
British Columbia: health-authority filing records
For applicable systems, an Authorized Person files plans and specifications with the regional health authority before construction. After completion, the regulation requires a letter of certification, as-built plan and maintenance plan. Ask the health authority about the filing for the property and compare it with the owner's copies. Municipal utility records separately help establish whether the property is connected to public sewer.
Alberta: find the Safety Codes permit issuer
Private sewage falls under Alberta's Safety Codes framework. An accredited municipality may administer the permit, while another safety-codes authority can apply elsewhere. Ask the municipality which authority had jurisdiction when the system was installed, then request the permit and inspection record from that issuer. A municipal building file alone may not contain the private-sewage approval.
Ontario: find the Part 8 principal authority
Most qualifying residential sewage systems at or below 10,000 litres per day fall under Part 8 of the Building Code. The principal authority is often the municipality but can be a health unit or conservation authority. Ask the correct office for the sewage permit, plans/site information and inspection or completion material it holds. For larger or otherwise provincially regulated works, the environmental approval route differs.
Québec: start with the municipality
Québec requires local municipalities to apply the isolated-residence wastewater regulation. Ask the municipal permit office for the permit/certificate, site-characterization report, plans, inspection material and any municipal septic-emptying or compliance records. Local programs genuinely differ, so use the municipality for the exact property rather than assuming a province-wide records process.
Atlantic provinces use different custodians
Nova Scotia's environment program uses notifications or approvals and recognized onsite professionals. New Brunswick's Technical Inspection Services handles provincial onsite approvals and inspections. Newfoundland and Labrador uses Government Service Centre/public-health approval for qualifying private systems, supported by an Approved Designer's site evaluation and design. PEI uses licensed site assessors and contractors within its provincial system. Ask for the approval/notification, design or assessment, inspection/completion record and any later alteration file.
Prairie provincial programs
Manitoba administers onsite wastewater registrations through Environment and Climate Change and certifies installers. Saskatchewan's private sewage works program is administered through public-health authorities, with specific exceptions identified by the province. In both cases, the provincial route can be more important than the city building file.
Reconcile the paper file with the property
A historical approval proves what was authorized at that time, not what condition the system is in today. Use a qualified onsite professional to locate components and compare the current installation with the file. Missing records should be treated as uncertainty rather than proof that a system is illegal or approved.