The three year deadline on a prior approval
A planning permission must be begun within three years. A Part 3 prior approval must be completed within three years of the prior approval date, and the condition sits in the Order where nobody can vary it.
A planning permission has to be begun within three years. A prior approval under Part 3 of the General Permitted Development Order has to be finished within three years. That one word is the difference between a scheme that is safe once the first trench is dug and a scheme that becomes unauthorised on a fixed calendar date whatever stage it has reached. The prior approval three year deadline runs from the prior approval date, not from the day you start, and nobody sends a reminder.
Why prior approvals carry their own time limit
A prior approval is not a planning permission granted by the authority. It is permission granted by the Order itself, subject to conditions written into the Order, with the authority's role limited to approving specified matters. So the familiar machinery of section 91 of the Town and Country Planning Act 1990 does not apply.
Instead the relevant Part 3 classes carry a condition in their own terms requiring the development to be completed within a period of three years starting with the prior approval date. Class MA, Class M, Class Q and the other residential conversion rights in Part 3 all work this way, with the wording varying slightly between classes.
Paragraph X of Part 3 defines the prior approval date, and it is not always the date on the decision notice. It can be the date the authority gave prior approval, the date it notified you that prior approval was not required, or the date the determination period expired without any decision at all. That last route catches developers who relied on deemed approval and never wrote the date down.
The condition requiring development to be completed
Read the condition on your own class rather than working from memory, because the deadline is the thing that gets diarised wrongly. Three points matter.
The period starts with the prior approval date, so delay in appointing a contractor eats into it. The obligation is completion rather than merely starting, so a 70 per cent complete building at the deadline has not satisfied the condition. And the condition sits in the Order, which means the authority cannot waive it, extend it or vary it on request.
| Consent | Time obligation | Can it be extended |
|---|---|---|
| Planning permission under section 91 | begin within three years | by a fresh application, and the permission survives once lawfully begun |
| Part 3 prior approval | complete within three years of the prior approval date | no, the condition is in the Order |
| Listed building consent | begin within three years | by a fresh application |
What counts as completion
The Order does not define completion, which is the first problem. In practice authorities look for a building that is finished and capable of occupation, and the evidence they accept tends to be the Building Regulations completion certificate, the date of first occupation, the council tax banding or a final certificate from the contract administrator.
Residual snagging, landscaping and a missing kitchen worktop are unlikely to trouble anyone. An unglazed opening, an unfinished staircase or a flat with no sanitary fittings is a different matter, because the test officers apply is whether the development described in the prior approval has actually been carried out.
Where a scheme creates several units, think about whether the right permitted development of the whole building or of each dwelling. The answer shapes whether you can complete part in time and argue about the rest.
Starting but not finishing in time
Here the law is thinner than anyone would like. With a planning permission, lawful implementation before the deadline keeps the permission alive indefinitely. With a prior approval, the Order simply imposes a completion deadline and says nothing about the status of work already carried out when that date passes.
That is a genuine gap rather than a trick question, and it is why the cautious advice is to treat the date as hard. Once it passes, the authority's view is likely to be that the development was not permitted by the Order, which makes it a breach of planning control, enforceable in the ordinary way under Part VII of the 1990 Act subject to the time limits in section 171B.
Two consequences follow for anyone funding or buying a part-built conversion. The building may not be lawful residential accommodation, and a warranty provider or lender may not accept it. Diligence on a part-complete Part 3 scheme should always start with the prior approval date and the Building Regulations record, not with the drawings.
Extending or renewing the position
You cannot vary the condition. Section 73 of the 1990 Act lets an applicant apply to develop without complying with a condition previously imposed on a planning permission, and a condition written into a development order is not that. So the options are narrower.
- Submit a fresh prior approval application before the deadline, which resets the three year period if the qualifying conditions are still satisfied.
- Apply for full planning permission for the completed scheme, with a Planning Statement that explains the history and the planning merits.
- Apply for a lawful development certificate under section 191 of the 1990 Act if you believe the position is already lawful.
The first route is often closed by the qualifying conditions rather than by the deadline. For a commercial to residential conversion the Class MA vacancy and continuous use conditions have to be satisfied again at the date of the new application, and a building that has been a building site for two years cannot show three months of vacancy preceded by two years of continuous Class E use. For an agricultural building the equivalent problem is proving the qualifying agricultural use all over again.
So the realistic answer for a stalled scheme is usually a full application. Budget for it.
Evidence of the date development began
Keep a dated record from the start, because the burden of showing compliance falls on you.
- The prior approval decision notice, or the dated acknowledgement and the calculation of the determination period where approval was deemed.
- Site photographs with reliable dates at the start, at each main stage and at completion.
- Building control records: initial notice or full plans approval, inspection records and the completion certificate.
- Contractor invoices, delivery notes and the building contract with its dates.
- Utility connection records and the council tax banding correspondence.
A statutory declaration from the site manager is worth having where the paper record is patchy. It is not a substitute for the paper record.
Falling back on a full application
A full application for a scheme that has overrun is not a defeat, and it has one advantage worth stating plainly. Prior approval limits the authority to a closed list of matters, which also limits what you can rely on. A full application lets you put the planning balance, the housing contribution and the quality of the scheme in front of the officer, and it can authorise the building works that strayed outside what was reasonably necessary under the right.
Expect to deal with matters the prior approval route never raised: amenity, overlooking, parking, refuse, and in most authorities biodiversity net gain. Those take time to assemble, so start them while the contractor is still on site rather than after the deadline has gone.
A Lawful Development Certificate under section 191 or 192 of the Town and Country Planning Act 1990 is the only formal way to confirm that development is lawful. This is general guidance rather than legal advice, so check the position with your local planning authority or a qualified professional before relying on it.
Enter your postcode on PlanScope to see which of the 66 report types a retrospective full application for your site is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
When does the three year period for a prior approval start?
It starts with the prior approval date as defined in paragraph X of Part 3 to the GPDO 2015. That can be the date the authority gave approval, the date it told you approval was not required, or the date the determination period expired without a decision. Developers relying on deemed approval often fail to record which date applies.
Can a local planning authority extend the three year completion period?
No. The condition is imposed by the General Permitted Development Order rather than by the authority, so it cannot be waived or varied, and section 73 of the Town and Country Planning Act 1990 does not reach it. The options are a fresh prior approval application before the deadline or a full planning application.
What happens if the conversion is only part finished at three years?
The Order imposes a completion deadline and says nothing about work already carried out, which is a genuine gap. The practical risk is that the authority treats the development as not permitted by the Order, and therefore as a breach of planning control enforceable under Part VII of the 1990 Act, subject to the section 171B time limits.
How do councils decide whether a scheme was completed in time?
There is no statutory definition, so officers look at whether the development approved has actually been carried out and the building is capable of occupation. The usual evidence is the Building Regulations completion certificate, the date of first occupation, the council tax banding and the contract administrator's final certificate.
Can I simply reapply for prior approval to reset the clock?
Sometimes, and only if the qualifying conditions are still met at the date of the new application. For Class MA the vacancy and continuous prior use tests have to be satisfied again, which a building site cannot usually do. Where that route is closed, a full planning application is the realistic fallback.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.