Bat mitigation licences and the three derogation tests

A bat mitigation licence is granted by Natural England under Regulation 55 of the Conservation of Habitats and Species Regulations 2017, and it turns on three tests that have nothing to do with the planning balance. Purpose, no satisfactory alternative, and no detriment to favourable conservation status. A scheme can have planning permission, strong policy support and a supportive officer, and still fail the second test because a different design would have avoided the roost.

Consultants get caught out by the sequencing rather than by the substance. The licence is applied for after permission is granted, but the tests have to be capable of being satisfied before permission is granted, because the planning authority is required to consider whether a licence is likely to be forthcoming. Leaving the derogation case until after the decision is how schemes end up consented and unbuildable.

Where the licence sits relative to planning permission

The two regimes are separate. Planning permission authorises the development in land use terms. The licence authorises what would otherwise be an offence: damaging or destroying a breeding site or resting place of a European protected species, or deliberately disturbing bats in a way that affects their ability to survive, breed or rear young.

Natural England will normally expect planning permission to be in place before it determines a licence application, and will expect any planning conditions relevant to the licensed activity to have been discharged. That puts the licence at the end of the consenting sequence and at the start of the construction one.

There is no route around it. If a roost will be affected, the licence is required whatever the permission says, and the offence is committed by the person carrying out the works. A protected species survey and any licence application must be carried out by a suitably licensed ecologist. That is a legal requirement, and an AI-assisted draft can structure the supporting documents but cannot replace the licensed person's judgement.

The three tests

Every licence application has to satisfy all three, and each is assessed independently.

The first is purpose. The activity must fall within one of the purposes the Regulations allow. For development, the usual purpose is imperative reasons of overriding public interest, including those of a social or economic nature, or the preservation of public health or public safety. The case has to be made with evidence about what the development delivers, not asserted.

The second is that there is no satisfactory alternative. This is the test that fails schemes. It asks whether the objective could reasonably be achieved in another way that would avoid or reduce the effect on the species: a different layout, retaining the roof structure, converting rather than demolishing, phasing the works differently, or doing nothing. Saying that the alternative would cost more is not enough on its own.

The third is that the action will not be detrimental to the maintenance of the population of the species concerned at a favourable conservation status in its natural range. In practice this is where the mitigation and compensation design is examined: does what you are providing maintain the local population.

How a planning authority applies the tests itself

The courts have held that where a proposed development would be likely to offend the protection given to European protected species, the planning authority must itself consider whether a licence is likely to be granted, rather than treating licensing as someone else's problem. The High Court reached that conclusion in R (Woolley) v Cheshire East Borough Council, and the Supreme Court considered the authority's duty further in Morge v Hampshire County Council, which recognised that an authority can generally place weight on Natural England's view where the regulator is content.

The practical effect for a consultant is that the ecology chapter should address the three tests explicitly, in those words, with the evidence for each. Officers who see that framing can write a report that survives scrutiny. Officers who see a mitigation strategy with no derogation case have to ask for one, which costs weeks.

Authorities also have a duty to have regard to the requirements of the Habitats Directive in exercising their functions, which is the hook on which the whole argument hangs.

What Natural England expects to see

The application package is substantial, and incomplete packages are the main cause of delay.

• Survey results to the current good practice guidelines, with the survey effort proportionate to the suitability of the building and the season the surveys were done in.
• A description of the roost: species, roost type, numbers, location within the structure, and the conditions that make it suitable.
• A reasoned statement addressing each of the three tests separately.
• A method statement setting out the works, the sequence, the exclusion technique, supervision arrangements and the licensed person responsible.
• The mitigation and compensation design, drawn rather than described.
• A monitoring programme with defined years and reporting.
• Evidence of planning permission and of discharge of relevant conditions.

Natural England publishes a service standard for determining licence applications, measured in working days. Check the current figure when programming, and allow for the clock stopping while further information is provided.

Designing mitigation and compensation

The principle is replacement of what is lost, matched to the roost being affected rather than to a catalogue.

Match the roost type. A crevice roost behind hanging tiles is replaced by crevice provision in the new fabric, not by a box on a pole. Match thermal conditions, which means paying attention to orientation, insulation, void size and the path light takes. Match access, because bats return to the position they know, and a new access point 4m from the old one may not be found. Maternity roosts need volume, warmth and a clear flight line, and they are the hardest to replace convincingly.

Integrated provision within the new building generally outperforms external boxes, and it survives the ownership changes that see boxes taken down. Where a roost of higher conservation significance is affected, expect Natural England to want a purpose-built structure rather than an integrated feature, and expect a longer monitoring commitment.

Do not confuse this with biodiversity net gain. Roost compensation is a legal requirement under the licensing regime, and it sits outside the statutory metric that drives a Biodiversity Net Gain Assessment. Counting the same provision twice is a common error and an obvious one to a reviewer.

Timing and the build programme

The licence will specify when works may be carried out, and the windows are narrow.

Works affecting a maternity roost are generally excluded during the maternity season, and works affecting any roost are excluded during hibernation. That typically leaves spring and early autumn for the destructive works, which then has to line up with the surveys that can only be done between May and September, and with a licence determination period that runs in working days.

Sketch the sequence backwards from the site start: bat survey inspection in winter, emergence surveys the following summer, planning submission in autumn, decision, condition discharge, licence application, licence granted, works in the following spring window. That is roughly 18 months from first inspection to first roof tile removed, and clients need to hear it early. Householders converting a loft face the same calendar on a smaller scale, as bats in your loft explains.

Where the effects are small, a low impact class licence can shorten the process considerably, but it is only available for defined circumstances and only registered ecologists may use it.

Why applications are refused or returned

The recurring reasons are consistent: survey effort below the recommended level for the suitability category, surveys carried out outside the season, the three tests addressed as a single paragraph rather than separately, compensation that does not match the roost lost, no monitoring proposed, planning conditions not discharged, and the alternatives question answered with cost alone.

Address all seven before submission and the process is administrative rather than adversarial. The habitat baseline that supports all of it usually comes from a Preliminary Ecological Appraisal done early enough to matter.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.