Reading a CIL charging schedule and working out liability

A CIL charging schedule calculation is simpler than its reputation. The chargeable amount is the rate multiplied by the chargeable area, adjusted by two index figures. Everything that goes wrong goes wrong in the area, because that is where existing floorspace offsets, measurement conventions and exemptions all operate.

If you are building one house or extending your own, the figures below may come to nothing at all. Several exemptions take small residential projects out of the charge entirely, and they depend on paperwork rather than on the arithmetic.

What a charging schedule contains

A charging schedule is a short document, usually two or three pages plus a map. It sets out the rate or rates in pounds per square metre, the geographical zones those rates apply to, the development types or uses each rate covers, and the date the schedule took effect.

The date matters as much as the rate. It is one of the two inputs to the indexation calculation, and a schedule adopted years ago will produce a different answer from one adopted recently at the same headline rate.

Alongside the schedule, look for three other published documents: the zone map at a scale that lets you locate your site, the authority's instalment policy, and its list of what the levy is intended to fund. The last of those used to be a formal requirement and is now usually published as part of the annual infrastructure funding statement, which our note on infrastructure funding statements covers.

Zones, uses and differential rates

Differential rates are permitted, and most schedules use them. Common splits:

• By geography, with higher rates where sales values support them and nil or low rates in regeneration areas.
• By use, with separate rates for residential, retail, offices, hotels, student accommodation and other categories.
• By residential type, where a schedule distinguishes houses from flats.
• A nil rate for uses the authority has decided not to charge, which is not the same as an exemption.

Check which zone and which use category your scheme falls into before doing anything else, and check it against the map rather than against a postcode. Zone boundaries follow ward or policy boundaries that do not always match what you would expect, and a site on a boundary is worth confirming with the authority in writing.

Mixed schemes are charged by applying each rate to the floorspace in that category and adding the results. A ground floor shop with flats above generates two calculations.

The chargeable amount formula

Schedule 1 to the Community Infrastructure Levy Regulations 2010 sets out the formula. In plain terms:

Chargeable amount equals the rate, multiplied by the chargeable area, multiplied by the index figure for the year permission was granted, divided by the index figure for the year the charging schedule took effect.

So four inputs: the rate from the schedule, the chargeable area, and two index figures. The chargeable area is the gross internal area of the chargeable development, less any existing floorspace that qualifies for offset.

An illustrative example, with arbitrary figures used to show the method rather than any real schedule. A new dwelling of 150 square metres gross internal area, in a zone charged at £100 per square metre, with no existing floorspace to offset, gives a base figure of £15,000 before indexation. If the index has risen by a fifth since the schedule took effect, the chargeable amount becomes £18,000. Treat the arithmetic as illustrative and take the real rate and index figures from the authority and the published index.

Gross internal area is the measure, and the Regulations do not prescribe a measuring standard, so disputes about what is included are common. Measure consistently, using a recognised code of measuring practice, and state on the submission which convention you used.

Indexation, and which index applies

The index was changed by amendment in 2019. Earlier schedules were indexed against an all-in tender price index, and the Regulations now specify an annual index published by the Royal Institution of Chartered Surveyors for levy purposes.

Two practical points. Use the figure for the calendar year in which planning permission was granted, not the current year, and use the figure for the year the schedule took effect as the denominator. Mixing years is the most frequent indexation error, and it runs in the authority's favour about half the time.

Where a liability notice has been issued with an index figure you cannot reproduce, ask the authority which year it used for each figure. That single question resolves most indexation disputes.

Existing floorspace and the six month rule

This is the most valuable part of the calculation for anyone working on an existing building.

Floorspace in an existing building can be deducted from the chargeable area where the building has been in lawful use for a continuous period of at least six months within the three years ending on the day planning permission first permits the development. The deduction applies to retained floorspace and to floorspace you are demolishing, provided the use test is met.

The evidence is what matters:

1. Business rates records, utility bills, lease or tenancy documents, and dated photographs.
2. A measured survey of the existing building with the gross internal area calculated on the same convention as the proposal.
3. Confirmation that the use was lawful, which for a long-empty agricultural or commercial building is sometimes the harder point.

A building vacant for more than two and a half years before permission will usually fail the test, which is why conversion schemes are sometimes charged on their full floorspace. If you are buying a vacant building to convert, the clock is a due diligence item.

Mezzanine floors inserted into an existing building are excluded from chargeable development below a floorspace threshold set in the Regulations, which is a useful point on industrial fit-outs.

Exemptions a small project should check

Four exemptions take most small residential work out of the charge, and all four depend on claiming before work starts.

Each one has conditions, and the sequence is unforgiving: assume liability, claim the exemption, wait for the acknowledgement, give notice of the start date, then begin. Skipping a step can cost the whole relief.

Instalments, and challenging the figure

Charging authorities may publish an instalment policy, and most do. It only operates where liability has been assumed and the authority has been told the start date, so a self-builder who misses those steps pays the whole sum shortly after work begins.

If the liability notice looks wrong, there is a defined route and the deadlines are short. A request to the charging authority to review the chargeable amount has to be made within 28 days of the notice. An appeal to the Valuation Office Agency on the calculation follows within 60 days. Separate appeal routes exist for apportionment, surcharges and deemed start dates, and the current time limits should be checked in the Regulations because they have been amended more than once.

A section 73 application to vary a permission generates a fresh calculation, with provisions designed to stop you paying twice for the same floorspace. Reconcile the areas after any variation rather than assuming the original figure holds. Where the scheme also carries planning obligations, check that the levy is not funding the same infrastructure, a point our note on section 106 monitoring fees touches on from the other direction.

Before you submit a planning application, download the charging schedule and the zone map, work out your chargeable area, and identify which exemption you intend to claim. You can see PlanScope pricing if you want to draft the supporting documents yourself, or browse the report types by category first.

This is general guidance, not legal advice. Check the position with your collecting 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.