Maybe you didn't realise you needed permission. Maybe your builder said it was fine. Maybe you inherited the problem when you bought the house. Whatever the reason, you now have work on your property that may not have the right approval - and you need to know what happens next.
The first thing to know: building without planning permission is not a criminal offence. It's a breach of planning control, not a crime. The consequences only become serious if the council takes enforcement action and you ignore it.
If the council becomes aware of unauthorised development - through a neighbour complaint, a site visit, or a sale falling through - they have several options. They don't have to take action. Planning enforcement is discretionary, and many councils only pursue breaches that cause genuine harm or where there's been a complaint.
Enforcement warning notice: The council may write to you inviting you to submit a retrospective planning application. This is the most common first step. It's not a formal legal action - it's an invitation to regularise the situation.
Enforcement notice: If the council decides the breach is serious, it can issue a formal enforcement notice. This specifies what the breach is, what you must do to fix it (modify the work, remove it, or restore the site), and the deadline for compliance. You typically get 3-6 months.
Prosecution: Failing to comply with an enforcement notice is a criminal offence. The council can prosecute, and fines can be substantial. In extreme cases, the council can carry out the remedial work itself and charge you for it.
The breach isn't the crime. Ignoring the enforcement notice is.
Option 1: Check if it's actually permitted development. Many projects that homeowners worry about turn out to be PD after all. If the work meets the conditions, you don't need retrospective permission - you need a Lawful Development Certificate (£274) confirming it was lawful all along. This is the simplest and cheapest route. See our LDC guide.
Option 2: Apply for retrospective planning permission. If the work genuinely needed planning permission, you can apply after the fact. The process and fee (£548) are identical to a normal application. The council assesses it on its merits. If the work would have been approved, it usually will be. See our retrospective planning permission guide.
Option 3: Wait for the 10-year rule. Since 25 April 2024, all planning breaches in England have a single 10-year enforcement window. This applies to work completed on or after that date. Work completed before 25 April 2024 still benefits from the previous 4-year enforcement window for building operations. If the work has existed continuously for the required period without enforcement action, it becomes immune. You can then apply for a Certificate of Lawful Existing Use or Development (CLEUD) for £274. But this requires strong evidence - dated photographs, utility records, satellite imagery - and does not apply to listed buildings, which have no time limit.
Think the work might actually be permitted development? A free eligibility check takes about two minutes and could save you the cost of a retrospective application.
Most homeowners don't find out about a planning issue from the council. They find out when they try to sell. The buyer's solicitor checks the planning history and asks about any extensions, loft conversions, or outbuildings. If the work doesn't have planning permission or an LDC, the solicitor flags it - and the sale stalls.
At that point, your options are: apply retrospectively (which delays the sale by 8+ weeks), take out indemnity insurance (which covers the buyer against future enforcement action but doesn't actually resolve the underlying breach), or reduce the price to reflect the risk. None of these are ideal. The cheapest solution is to regularise the work before you put the house on the market.
The council won't send someone round without warning. Enforcement begins with a letter or notice. You have time to respond and take advice.
You won't go to prison for an extension. Criminal penalties only apply for ignoring an enforcement notice after it's been served. The breach itself is not a criminal matter.
The council won't automatically make you demolish the work. Most enforcement action starts with an invitation to apply retrospectively. Demolition or removal is a last resort, usually reserved for cases where the work causes genuine harm and can't be made acceptable through modification.
Building regulations approval doesn't mean you have planning permission. These are completely separate systems. Having building control sign-off does not protect you from planning enforcement, and vice versa.
Common mistakes that cost money
Doing nothing and hoping nobody notices. It will surface when you sell. Every time. The buyer's solicitor will find it. Fixing it now costs less than fixing it under the pressure of a sale.
Assuming the 10-year rule applies to listed buildings. It doesn't. There is no time limit for enforcement against unauthorised works to a listed building. If you own a listed property with unauthorised alterations from any era, you are liable.
Applying for retrospective PP when the work was actually PD. Check the permitted development rules first. An LDC costs £274 and cannot be refused if the conditions are met. A planning application costs £548, takes longer, and can be refused.
PD Assessment Tool
Before assuming the worst, check whether the work qualifies as permitted development. If it does, you don't need retrospective permission at all - just a Lawful Development Certificate. Our free eligibility check covers property type, designated area status, and the key PD conditions for your project type.
Free eligibility check. Full assessment £47.
Content verified against the Town and Country Planning Act 1990, sections 171A-196D (enforcement), and GOV.UK National Planning Practice Guidance on enforcement (updated 2024). Time limit changes verified against the Levelling Up and Regeneration Act 2023 (effective 25 April 2024). This page is for general information only and does not constitute legal advice.
April 2026