A completion certificate is the document that formally closes out a building regulations application. It tells the world — and specifically your conveyancer, mortgage lender and insurer — that the finished work was inspected and found to comply with the Building Regulations in force at the time. Without it, that assurance disappears entirely.
Most homeowners only discover they need one when they try to sell. Solicitors routinely raise a requisition if building work was carried out without evidence of sign-off, and buyers’ lenders can refuse to proceed. Understanding what a completion certificate is, when you need it and what to do if one is missing can save you serious delay and expense.
What is a completion certificate?
When you notify building control of work that requires regulation approval — an extension, loft conversion, new staircase, electrical rewiring, reroofing, or structural alteration, among others — you are opening a building regulations application. An inspector from either your local authority building control (LABC) or a private approved inspector (now called a Registered Building Control Approver, RBCA, under the Building Safety Act 2022) then makes visits at key stages: foundation, damp-proof course, structural frame, roof structure, insulation and so on.
Once the work reaches practical completion, you request a final inspection. If the inspector is satisfied, they issue a completion certificate. In England and Wales, LABC certificates are issued under Regulation 17 of the Building Regulations 2010. Private RBCAs issue an equivalent final certificate under Regulation 20.
In Scotland the equivalent document is a completion certificate issued under the Building (Scotland) Act 2003; in Northern Ireland it is a certificate of completion under the Building Regulations (Northern Ireland) 2012.
When do you need one?
You need a completion certificate for any notifiable building work, which broadly covers:
- Structural alterations (removing load-bearing walls, opening up floor joists, new lintels)
- Extensions and outbuildings over certain thresholds
- Loft, garage or basement conversions
- New bathrooms or kitchens involving drainage
- Replacement of heating systems, including boiler swaps and heat pump installations
- Electrical installation work that is notifiable under Part P
- New staircases and balustrades
- Underpinning
Permitted development work that is also notifiable — a rear extension, for instance — still requires building regulations sign-off even though no planning permission was needed.
Why it matters for property transactions
Conveyancers check for completion certificates as standard because they represent a legal warranty of sorts. A mortgage lender will not rely on a structural surveyor’s opinion alone; they want documented evidence of regulatory compliance. If you cannot produce a completion certificate, a buyer’s solicitor will typically ask for one of three things: a regularisation certificate from the local authority, a copy of the original approval and inspection records, or indemnity insurance.
Indemnity insurance covers the buyer and their lender against the risk of the local authority issuing an enforcement notice — but it is not the same as a completion certificate and should be a last resort rather than a standard workaround.
Costs and timescales
| Route | Typical cost | Timescale |
|---|---|---|
| New building regulations application (notifiable work underway) | £200–£1,200 depending on project size | Weeks to months |
| Regularisation certificate (retrospective, LABC only) | £200–£600 for most domestic projects | 4–12 weeks |
| Indemnity insurance (instead of regularisation) | £100–£500 one-off premium | 1–5 working days |
| Approved inspector (RBCA) final certificate | Included in contract fee, typically £300–£800 all-in for minor works | Subject to inspection |
Local authority fees vary: a London borough will charge more than a rural district council. The regularisation route requires the building owner to expose sufficient areas of the work for inspection — reopening plastered walls or lifting floors — which adds contractor costs on top of the council fee.
What to do if a completion certificate is missing
Step 1 — Search your local authority records. Building control records are not always indexed under the current owner’s name. Call the LABC and provide the property address and approximate date of the works. Many councils have digitised records going back to the 1980s; others can search paper files. There is no fee for this search.
Step 2 — Check with the original approved inspector. If an RBCA was used, their final certificate would have been deposited with the local authority. The RBCA may also hold copies; the sector has seen consolidation, but records often transfer to successor firms.
Step 3 — Apply for a regularisation certificate. This is available only from LABC (not private RBCAs) and only for work completed after 11 November 1985. You submit plans, a description of the work and photographs, and the inspector may require opening-up works. On satisfactory inspection, the authority issues a regularisation certificate — legally equivalent to a completion certificate for conveyancing purposes.
Step 4 — Consider indemnity insurance. If the work is old (pre-1985, or more than 12 years old in many cases), if opening up is impractical, or if the transaction timeline is tight, indemnity insurance is often the fastest resolution. Premiums are typically paid once by the seller. Note that contacting the local authority after deciding to go down the insurance route can invalidate the policy — seek legal advice first.
Selling a property with missing completion certificates
Disclose the issue to your solicitor at the outset. They will assess which route is most appropriate depending on the age and nature of the works, the buyer’s lender requirements and the urgency of exchange. Trying to hide a missing certificate is not only ethically wrong but contractually risky — it can give a buyer grounds to rescind after exchange.
Building Safety Act 2022 changes
The Building Safety Act 2022 reformed building control in England. From April 2024, private approved inspectors became Registered Building Control Approvers regulated by the Building Safety Regulator. Higher-risk buildings (HRBs — residential buildings over 18 m or 7 storeys) face a more stringent Gateway process, with a final completion certificate issued only after the Regulator is satisfied the Golden Thread of information is in place. For most domestic renovation work, the practical impact is limited, but it is worth noting that the regulatory landscape has shifted.
Practical tips
- Request your completion certificate the moment the inspector approves the final inspection. Builders sometimes move on and final paperwork is never requested.
- Keep all building regulations documentation together with your title deeds or in a dedicated home file — a solicitor will thank you, and you will thank yourself at sale time.
- If you are buying a property with recently completed extensions or conversions, always ask your solicitor to requisition the completion certificate rather than accepting the seller’s assurances.
- For work that genuinely did not require building regulations approval (most like-for-like repairs, painting and decorating, fitting kitchens without drainage changes), there is no completion certificate to obtain — a letter from a suitably qualified building professional confirming the exemption can be helpful instead.
