Missing Planning Permission: Will It Stop Your Mortgage?

Unauthorised works are one of the most frequently encountered issues in UK residential property transactions. Extensions built without planning permission, loft conversions carried out without approval, outbuildings erected in breach of permitted development limits — the list is long and surprisingly common. The question buyers and their solicitors face is a practical one: does it matter, and can you still get a mortgage?

The answer is almost always yes, you can get a mortgage — but how you get there depends on the type of works, when they were done, and whether the immunity period has passed.

The Two Core Planning Immunity Rules

Planning enforcement in England and Wales is subject to time limits. Once these limits pass, the local planning authority loses the power to take enforcement action. This is the legal foundation on which the indemnity insurance market is built.

The 4-Year Rule (Operational Development)

Under section 171B of the Town and Country Planning Act 1990, enforcement action for operational development — which includes building operations such as extensions, new buildings, and structural alterations — becomes time-barred after four years from the date the operations were substantially completed.

If an extension was built in 2015 without planning permission and it is now 2026, the council cannot take enforcement action. The extension is effectively immune from planning enforcement.

The 10-Year Rule (Change of Use)

Where the issue is a material change of use — for example, converting a single dwelling into flats, or converting a garage to a habitable room — the enforcement time limit is ten years from the date the breach began.

The longer period reflects the fact that changes of use can have broader planning implications, and the policy position is that these should remain challengeable for longer.

What the Clock Actually Starts From

The clock starts from the date the breach began:

• For operational development: from when the works were substantially complete
• For change of use: from when the use changed

Evidence of the start date matters. Planning enforcement officers can challenge claimed start dates if there is evidence to the contrary. Planning history, building regulations applications, estate agent particulars from the time, photographs, and neighbour recollections can all be relevant.

Certificate of Lawfulness

A Certificate of Lawfulness (formally a Lawful Development Certificate under section 191 of the TCPA 1990) is an official certificate from the local planning authority confirming that a specific use, operation, or activity is lawful for planning purposes.

There are two types relevant to existing situations:

Certificate for Existing Use or Development (Section 191)

This certificate confirms that an existing use or completed building operation is lawful. To obtain it, the applicant submits evidence to the local planning authority demonstrating that the immunity period has passed.

If granted, this is conclusive evidence that planning enforcement cannot be taken. It is highly valuable because it:

• Removes the uncertainty entirely
• Cannot be challenged once issued
• Transfers with the property permanently
• Is often preferred by lenders over indemnity insurance

The application requires evidence — typically statutory declarations from neighbours, aerial photographs, utility records, or other documentation proving the works predate the immunity period. It costs around £206 (the standard planning fee for existing dwellinghouse applications in England, as of 2026) and takes up to 8 weeks.

Why It Is Not Always Pursued

Despite being the most definitive solution, Certificates of Lawfulness are not always obtained, for several reasons:

• Evidence availability: For works carried out decades ago, documentary evidence can be difficult to assemble.
• Transaction timeline: The 8-week determination period does not fit many completion timescales.
• Cost relative to indemnity: For most residential situations, indemnity insurance is cheaper and faster, and lenders accept it.

If a Certificate of Lawfulness already exists on the title, this is the best possible position — no indemnity insurance is needed.

Retrospective Planning Applications

Where the immunity period has not passed — typically where the works are less than four years old — the standard approach is a retrospective planning application.

This is an application for planning permission after the fact. The council considers it just as it would consider any planning application. The outcome may be:

• Approval: The permission is granted and the issue is resolved
• Refusal: The council refuses, and may then serve an enforcement notice requiring the works to be removed or altered

If works are less than 4 years old and a retrospective application has been refused, the position is serious. The property may be unmortgageable until the works are removed, altered to achieve approval, or until the immunity period passes.

Indemnity Insurance: The Standard Solution

For the vast majority of transactions involving unauthorised works where the immunity period has passed, indemnity insurance is the accepted route.

How It Works

An indemnity policy is a one-off, single-premium insurance policy that covers the buyer (and the lender) against the financial consequences of planning enforcement action. In practice, because enforcement is time-barred after the immunity period, the risk the insurer is taking on is very low — hence the low cost.

The policy typically covers:

• The cost of compliance with any enforcement notice (however unlikely)
• Loss of value if the property cannot be used as intended
• Legal costs in defending any enforcement action
• In some cases, the cost of demolition or alteration

Premiums are typically £100-300 for residential properties, paid once. The policy runs with the property and benefits all future owners.

Who the Policy Protects

Both the buyer and the mortgage lender are typically named on — or benefit from — the indemnity policy. This is important: the lender's security is protected, which is why most lenders accept an indemnity policy as a satisfactory resolution.

Obtaining an Indemnity Policy

Indemnity policies are arranged by solicitors through specialist legal indemnity insurers. The main providers include:

• Aviva
• Defaqto-rated specialist insurers such as CLS, First Title, and Landmark
• Solicitors' own preferred panel insurers

The solicitor acting for the buyer or seller will usually arrange this. In straightforward cases, a policy can be obtained within 24-48 hours.

The Critical Rule: Do Not Contact the Council

This is the most important practical point about indemnity insurance — and it is one that catches out buyers and sellers alike.

If you contact the local planning authority about the unauthorised works before a policy is in place, most indemnity insurers will refuse to provide cover — or will exclude the specific risk you have disclosed.

The reason is simple: an indemnity policy works on the assumption that the council is unaware of the breach. By contacting the council, you draw their attention to the matter and potentially prompt enforcement action — exactly the risk the policy is meant to cover against.

This means:

• Do not ring the council to ask whether the extension needed permission
• Do not make a pre-application enquiry about the works
• Do not submit a retrospective planning application unless you intend to see it through
• Do not contact the council at all until you have taken legal advice

Your solicitor will know this rule. But buyers sometimes contact the council themselves without realising the consequences. If you are considering a purchase with unauthorised works, speak to your solicitor before making any enquiries.

How Lenders Handle Missing Planning Permission

Lenders' responses to unauthorised works depend on the nature and scale of the issue:

Minor Residential Extensions (Within Immunity Period)

For straightforward cases — a rear extension built more than 4 years ago, with no indication of enforcement action — most lenders will accept an indemnity insurance policy as a satisfactory resolution. The policy needs to be in place and noted on the title. The lender's solicitors (acting under the CML/UK Finance Handbook) will confirm this requirement.

Change of Use and More Significant Works

Where the issue relates to a material change of use — a flat conversion, a garage conversion to a habitable room, or the division of a dwelling — lenders take a closer look. If the 10-year period has passed, an indemnity policy is generally accepted. If the period has not passed, the lender may decline or require the works to be properly authorised.

Structural Works Without Building Regulations Sign-Off

Planning permission and building regulations approval are separate requirements. A property can have planning permission but lack building regulations sign-off — or lack both. Building regulations compliance relates to the safety and structural integrity of the works. Some lenders are as concerned about missing building regs as missing planning permission. See our guide to building regulations sign-off for more on this.

Recent Unapproved Works

Works carried out within the last 4 years that have not been granted planning permission are much more problematic. The lender cannot rely on an indemnity policy (the immunity period has not passed) and a retrospective application may or may not succeed. Some lenders will decline until the issue is resolved; others will consider with conditions.

What Surveyors Report

The lender's valuer will note visible signs of alterations or extensions during the inspection. They do not assess planning compliance themselves, but their observations may prompt the lender to raise enquiries with the solicitors.

A surveyor who notes a substantial extension that looks relatively recent, or a property layout that differs significantly from what the planning register shows, may flag this in their report. This is one of the routes through which planning issues come to light in transactions.

In a full building survey, the surveyor may specifically raise planning compliance as a matter for the solicitor to investigate. This is standard good practice in a Level 3 survey.

Retrospective Planning: What It Involves

Where a retrospective application is the chosen route, the process is:

1. Pre-application enquiry (optional but useful) — some councils offer pre-application advice to assess the likely outcome before a formal submission. This is discretionary and comes at a cost.
2. Application submission — the application is submitted to the local planning authority with plans and any supporting information.
3. Consultation period — neighbours and statutory consultees are given the opportunity to comment (typically 21 days).
4. Determination — the council has 8 weeks to determine the application (or a longer agreed extension).
5. Decision — approval (retrospective permission granted) or refusal (with the risk of enforcement proceedings).

The cost depends on the scale of the works. For a standard householder application (extensions, outbuildings), the fee is £258 in England (as of April 2026).

Practical Steps for Buyers

1. Ask your solicitor to check the planning history — this is a standard part of conveyancing searches and should reveal any planning conditions, enforcement notices, or prior applications relating to the property.
2. Review the TA6 information form — the seller must declare any known issues, including unauthorised works. Check the replies carefully.
3. Do not contact the council yourself — if you suspect an issue, speak to your solicitor first.
4. Confirm what lender conditions apply — your solicitor will report on whether the lender requires a Certificate of Lawfulness or will accept indemnity insurance.
5. Factor in the cost — for most residential indemnity policies, the cost is modest (£100-300). For more complex situations, it may be higher.
6. Check building regulations separately — planning permission and building regulations approval are separate. If works are present, both need to be verified.

This is educational content, not financial advice. Your situation is unique — speak to a qualified mortgage broker and solicitor before making any decisions.