CIL Change of Use: Conversions and Existing Buildings

 

A CIL change of use can be surprisingly complicated. Converting an existing building does not automatically mean CIL is payable, but it does not automatically mean the development is free of CIL either. The result depends on what the planning permission allows, whether a new dwelling is created, the charging schedule and how the existing building is treated under Schedule 1.

This matters with office-to-residential conversions, Class MA, barn conversions, other permitted development changes of use and schemes where an existing building is retained rather than demolished.

 

When can a CIL change of use be chargeable?

 

The first question is whether the development falls within the CIL regime at all. A change of use which creates one or more dwellings can be chargeable development even if it creates no new external floorspace. The minor development exemption for less than 100 m² of new build does not apply where the chargeable development comprises one or more dwellings.

That does not mean the whole existing building will necessarily be charged. Schedule 1 then determines the deemed net area on which CIL is calculated, including any qualifying retained existing floorspace.

For a change of use which does not comprise a dwelling and creates less than 100 m² of new-build floorspace, the minor development exemption may mean no CIL is payable.

 

Existing floorspace can reduce the charge to zero

 

This is where many conversion schemes are won or lost. A retained existing building may reduce the CIL calculation if it falls within one of the deductions in Schedule 1.

An in-use building is a relevant building which contains a part that was in actual lawful use for one continuous period of at least six months within the three years ending on the day planning permission first permits the chargeable development.

If that test is met, qualifying retained parts can enter the K_R deduction. There is also a separate K_R route for some retained parts of other relevant buildings where the intended post-development use could have been carried on lawfully and permanently without further planning permission on the day before the first-permits date.

The quality of the evidence matters. Schedule 1 allows the collecting authority to deem a building not to be in use, or an area to be zero, where it does not have sufficient information of sufficient quality.

 

Permitted development does not switch CIL off

 

Planning permission granted by the GPDO is a general consent for CIL purposes. A development carried out under permitted development rights can therefore still be chargeable.

For chargeable development under a general consent, the developer normally has to submit a Notice of Chargeable Development, Form 5, before development starts. Regulation 8 makes the date the collecting authority receives that notice the usual first-permits date for the CIL calculation.

That date can be crucial because it fixes the three-year period used for the six-in-36 existing-building test. If no Notice of Chargeable Development is submitted, the collecting authority has powers to issue its own notice and the regulations provide a different first-permits trigger.

Our CIL forms guide explains Form 5 and the other CIL notices.

 

Class MA office-to-residential conversions

 

Class MA is a good example of why planning permission and CIL need to be considered separately. Prior approval may allow the change from Class E to residential use, but the creation of dwellings can still place the development within the CIL regime.

In R (Herod Property Ltd) v Westminster City Council [2026] EWHC 2122 (Admin), the developer believed retained in-use floorspace reduced the charge to zero. The High Court decision is a warning about starting work while assuming the collecting authority will accept your calculation. Once development has commenced, the ordinary regulation 113 review and regulation 114 appeal routes can be lost.

A 2025 VOA decision, CIL Appeal 1867784, is also useful. It concerned a Class MA office-to-residential conversion and reached a nil charge because the Appointed Person accepted a Schedule 1 retained-building deduction. That decision is fact-specific rather than a court precedent, but it shows why the exact first-permits date and the retained-use test matter.

 

Barn conversions and Class Q

 

A barn conversion creating a dwelling can also be within CIL even where the shell of the existing building is retained. The key questions include which planning permission is the chargeable development and whether the existing barn qualifies for a Schedule 1 deduction.

CIL Appeal 1889233, decided in June 2026, concerned retrospective permission for a barn changed to a dwelling. The Appointed Person explained that an earlier Class Q prior approval did not by itself remove the later retrospective permission from CIL. The earlier permission could still matter when applying Schedule 1 and deciding whether existing floorspace was deductible.

This is another fact-specific VOA decision, not binding case law, but it is a useful warning against assuming that an earlier permitted development route automatically settles the CIL position of a later permission.

 

Subdividing one dwelling is different

 

Regulation 6 contains a specific exclusion for changing a building previously used as a single dwellinghouse into two or more separate dwellinghouses. The subdivision itself is therefore not treated as development for CIL liability.

Be careful where the same planning permission also includes extensions or other chargeable work. The excluded subdivision does not necessarily remove CIL from a separate new-build element included in the scheme.

 

Mezzanines and internal works have their own rule

 

Regulation 6 also excludes certain works to an existing building where planning permission is required only because of section 55(2A) of the Town and Country Planning Act 1990.

In R (Orbital Shopping Park Swindon Ltd) v Swindon Borough Council [2016] EWHC 448 (Admin), the High Court held that CIL was not chargeable on a mezzanine permission falling within that exclusion. The council could not simply combine that permission with a separate permission for external works and treat the two as one chargeable development.

The case is a useful reminder that CIL follows the statutory definition of the development for which planning permission is granted. It is not enough to say that two permissions are commercially or functionally connected.

 

Retrospective conversion permissions need particular care

 

Where a conversion is regularised through retrospective planning permission under section 73A, regulation 7 treats the development as commencing on the day that retrospective permission is granted for CIL purposes.

Government guidance also makes clear that reliefs and exemptions cannot normally be obtained for section 73A development, apart from the minor development exemption. A conversion which might have produced a different CIL outcome if handled prospectively can therefore become much more expensive when regularised retrospectively.

 

Challenge the calculation before commencement

 

If the collecting authority does not accept your existing-building deduction or other part of the chargeable amount, the ordinary route starts with a regulation 113 review within 28 days of the Liability Notice. A regulation 114 appeal to the Valuation Office Agency must normally be made within 60 days of the original Liability Notice.

Do not start the development while relying on those routes. Commencement can prevent the review or appeal being made, or cause one already under way to lapse. See our CIL appeals guide.

If the underlying planning application or prior approval is refused, that is a separate planning matter. Depending on the route, normal planning appeal rights may be available.

 

Planning costs are separate from CIL

 

CIL is separate from the fee for a planning application, prior approval or certificate. The planning route and its fee depend on the change of use being proposed. See our planning application fees guide and Use Classes Index.

 

Relevant CIL rules and decisions

 

• Regulation 6: meaning of development for CIL
• Regulation 8: when planning permission first permits development
• Schedule 1: calculation of the chargeable amount
• VOA CIL appeal decisions

Community Infrastructure Levy (CIL)

 

CIL Change of Use Page Created: 30th August 2026