Working out CIL liability from a charging schedule

A cil liability calculation is arithmetic, not judgement. The charging authority publishes a rate in pounds per square metre, you measure the chargeable floorspace, you deduct any qualifying existing floorspace, and you apply the index figures for the year the charging schedule took effect and the year permission was granted. Every one of those four inputs is checkable, which is why a surprising number of liability notices turn out to be wrong when someone finally checks them.

Where the charging schedule lives

Community Infrastructure Levy rates are set by the charging authority in an adopted charging schedule, published on its own website alongside the local plan documents. Not every authority charges the levy, and those that do often set different rates by zone, by use and sometimes by unit size.

Read the schedule itself rather than a summary page. What you are looking for is the rate table, the zone map, the definitions of the use categories, the date the schedule took effect, and any instalments policy and exemptions policy published with it. Those last two are separate documents in many districts and they change the cash flow more than the rate does.

Check also whether the authority has adopted a newer schedule since the one in circulation. A revised schedule changes the index figure used in the calculation as well as the rate.

Measuring chargeable floorspace correctly

The chargeable area is gross internal area of the new build. Gross internal means measured to the internal face of the external walls, including internal walls, circulation, plant rooms and integral garages, and including every storey.

The measurements that cause disputes are these. Basements and roof spaces with headroom count. Integral garages count, detached ones usually do not, and the distinction turns on whether the space is within the building envelope. Covered but unenclosed areas such as open car ports are generally outside the measurement, but check the authority's stated approach.

Provide the measurement yourself on the CIL additional information form with a floor-by-floor schedule and the drawing references. Where the authority has to derive areas from your drawings, it will do so conservatively and you will be the one arguing afterwards.

Deductions for existing lawful floorspace

The deduction for retained or demolished buildings is where most of the money is, and it has a condition attached. The existing building must have been in lawful use for a continuous period of at least six months within the three years before development is permitted.

That test defeats a great many conversions of long-empty buildings. A barn empty for a decade, an office vacant since before the pandemic or a derelict shop all fail it, and the whole floorspace then becomes chargeable even though nothing new is being added.

Evidence the use. Business rates records, utility bills showing consumption rather than standing charges, tenancy agreements, staff records and dated photographs are the material that works. Assemble it before the application is submitted, because the deduction is calculated when the liability notice is issued and reversing it afterwards is slow.

Demolished floorspace within the same scheme is deducted on the same basis. Keep the pre-demolition measured survey.

There is a further wrinkle worth knowing. Where a building has been demolished before the application is made, the authority needs evidence of what stood there and how it was used, and an unrecorded demolition can quietly remove a deduction worth more than the rest of the scheme's professional fees put together. Measure and photograph before anything comes down.

Indexation and the figure that applies

The chargeable amount is the rate multiplied by the chargeable area, then adjusted by the ratio of two index figures: the index for the year in which planning permission was granted, divided by the index for the year in which the charging schedule took effect. An authority with an old charging schedule therefore charges considerably more than its headline rate suggests.

The index used for the levy is published annually, and the figure that applies is fixed by the calendar year of the grant of permission rather than by the date you start work. Two identical schemes permitted in consecutive years carry different charges.

This is the input most often got wrong in appraisals, because people take the rate from the schedule and stop there. Run the full formula, and state the index figures you used in your own working so that the liability notice can be checked against it line by line.

Differential rates by use and zone

Most schedules set different rates for residential, retail, and other uses, and many split the district into zones reflecting viability evidence from the examination. Mixed use schemes are apportioned by use.

Two traps recur. First, the use category in the charging schedule may not match the use class in the application, so read the definitions in the schedule rather than assuming. Second, zone boundaries follow lines drawn on a map at plan scale, and a site on the boundary needs confirming in writing.

Where a scheme includes affordable housing, social housing relief applies on the qualifying floorspace, and it has to be claimed. Our note on how a CIL charge is calculated for a new dwelling works through the arithmetic on a single plot.

The liability notice and checking it

The collecting authority issues a liability notice after permission is granted. Check five things against your own calculation: the chargeable area, the deduction for existing floorspace, the rate applied, the index figures, and the relief or exemption claimed.

Then check the procedural side, because that is where the money is lost. Someone must assume liability, and a commencement notice must be submitted before work begins. Missing either attracts surcharges and can remove an exemption entirely, which our note on CIL surcharges and how to avoid them sets out.

Self-builders have a specific exemption for a dwelling they build and occupy as their principal residence for three years, and residential extensions above the minor development threshold have their own exemption. Both must be claimed before commencement, both require the commencement notice, and both are lost by starting early. This is the single most expensive administrative mistake in the levy regime.

Relief and exemption claims each have their own form and their own timing. Submit them with the application or immediately after the grant, not when the contractor is on site.

Timing, instalments and disputes

Payment falls due on commencement unless the authority has an instalments policy, in which case the demand notice sets out the stages. Instalment policies are generous in some districts and non-existent in others, so read the published policy before you build the cash flow.

If you think the calculation is wrong, there is a formal route. Ask the authority for a review of the chargeable amount within the stated period, and if that does not resolve it, an appeal on the chargeable amount goes to the Valuation Office Agency, while appeals on surcharges and on deemed commencement go to the Planning Inspectorate. All of these have short deadlines that run from the date of the notice.

Illustrative example: a scheme of four houses with a total gross internal area of 520 square metres replacing a bungalow of 90 square metres that has been occupied throughout. The deduction applies, so the chargeable area is 430 square metres. The rate comes from the schedule, and the index ratio between the year of the schedule and the year of the grant adds a further uplift. Working that out before the land offer is made is what keeps the deal viable.

Budgeting the professional inputs alongside the levy is easier with fixed figures. PlanScope's pricing is one free report, £50 per report or £150 per month on the Professional tier.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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