The main in-use test requires at least part of the building to have been in lawful use for a continuous six months within the relevant three-year period. An empty structure is not automatically a credit against a new building. [1]
Start with the existing building and its use
The test concerns lawful use, not simply ownership or the fact that a building appears on a map. For demolition deductions, national guidance identifies the three-year period ending on the day planning permission first permits the development. Eligible buildings must also be demolished before the chargeable development is completed. [1]
This makes the sequence important. Before clearing the site, ask the CIL adviser to confirm whether the existing building needs to remain at the relevant permission date. Brentwood's published explanation expressly identifies the need for the existing floorspace to exist when permission is granted and for demolition to take place before completion. That is a useful explanation of the deduction rules, not a Brentwood tariff for a London or Epping project. [2]
Measure consistently
Use a measured gross-internal-area schedule showing what exists, what will remain, what will be demolished and what will be newly built. Form 1 asks for the information used to assess those areas. Reconcile its figures with the same version of the architectural drawings submitted for permission. [3]
Gross internal area is not simply the sum of room sizes advertised for sale. The local measuring guidance includes internal features and excludes specified external elements. Ask the person preparing the calculation to state the measurement basis and explain any unusual void, basement or shared area. [2]
Retained buildings have an additional distinction
Failure to meet the six-month lawful-use test normally prevents a deduction for demolition. However, national guidance provides a different possibility for retained parts: they may still be taken into account where their proposed use matches a use that could lawfully have occurred without a new planning permission. [1]
That exception is not a blanket allowance for every long-vacant building. Abandonment of a use and the legal position of the retained space require consideration. Give the assessor the actual history rather than labelling the entire property “existing lawful floorspace” without supporting it. [1]
A simple illustration, not a liability calculation
Suppose a scheme has 200 m² of relevant proposed floorspace and the authority accepts 120 m² of qualifying existing floorspace against it. Simple subtraction gives 80 m². Whether that is the correct chargeable area still depends on the statutory formula, development uses, permission and relief position. The illustration does not mean every replacement project pays on “new area minus old area”. [1][2]
The authority also applies the relevant CIL rate and index. Keep the floor-area calculation separate from the rate calculation so any disagreement can be identified clearly. [1]
Assemble the evidence before submission
A practical evidence file should contain measured existing drawings, dated photographs, the planning-use history and records supporting the claimed occupation period. Match that evidence to the building and period relied on, rather than submitting unrelated records simply because they have the same postal address. Form 1 requires the relevant building and use information to support the assessment. [3]
Keep the completed schedule and the authority's calculation with the permission. Where the design or permission changes, ask for the CIL position to be reviewed before assuming the original deduction remains available. [1]