Mayoral CIL: bands, rates and when it becomes payable
The Mayor charges a levy on new floorspace across all of Greater London, on top of the borough charge. The banding, the six-month lawful use deduction and the commencement notice decide what you actually pay.
Mayoral CIL is a charge on new floorspace levied by the Mayor of London across all 33 London boroughs and the City of London, on top of whatever the borough charges under its own Community Infrastructure Levy schedule. It is collected by the borough, calculated on net additional gross internal floorspace, and set by a charging schedule that puts each borough into a band. If you are appraising a London site, you are budgeting for two levies, and the Mayoral charge is the one people forget until the liability notice arrives.
The rates are index-linked and revised, so take the figures from the Mayor's current charging schedule rather than from a spreadsheet built two years ago.
What the Mayoral levy pays for
The Mayor charges under Part 11 of the Planning Act 2008 and the Community Infrastructure Levy Regulations 2010 as amended, in the capacity of charging authority for Greater London. The money is applied to strategic transport infrastructure, and the current levy was introduced to contribute to the Elizabeth line.
That purpose matters in one practical way. Because the Mayoral charge funds a named strategic project, it is not available to the borough for local infrastructure, and it does not reduce what the borough can seek through its own levy or through a section 106 agreement. Applicants sometimes argue that paying one levy should offset the other. It does not.
How the charging bands work
The schedule divides London into bands, with the highest rates in central boroughs and the lowest in outer London. A second set of rates applies to specified commercial uses in defined central and Isle of Dogs areas, where office, retail and hotel floorspace is charged at a higher rate than elsewhere.
Two features of the banding catch people out. The band follows the borough, not the site's character, so a low-density site in a high-band borough pays the high-band rate. And the commercial rates are defined by use and by area, so a mixed-use scheme can pay two different rates within one building, apportioned by floorspace.
| Step | What you need | Where it comes from |
|---|---|---|
| Identify the band | Borough and, for commercial floorspace, the charging zone | The Mayor's charging schedule |
| Establish chargeable floorspace | Gross internal area of new build by use | Measured GIA on the submitted drawings |
| Deduct existing floorspace | GIA of buildings in lawful use for six continuous months in the past three years | Evidence of lawful use, rates records, tenancy documents |
| Apply indexation | The index figure for the year in which planning permission is granted | The published index referred to in the CIL Regulations |
Calculating liability on a scheme
The chargeable amount is the net additional floorspace multiplied by the rate, adjusted by indexation. Net additional means new gross internal area less the gross internal area of existing buildings that qualify for deduction.
The deduction rule is where most of the money is won or lost. A building can only be netted off if it 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 chargeable development. A long-vacant building fails that test, and its floorspace is charged as though the site were empty. On a conversion of a building empty for years, that single rule can move the liability by a six-figure sum.
Evidence the use properly and early. Business rates records, utility accounts, tenancy agreements and dated photographs all help. If the building has been part-occupied, quantify which parts and for how long, because the deduction can be applied to the occupied portion.
Mezzanines, plant rooms and basements all count towards gross internal area, and structures that fall outside the definition of a building do not. Where a scheme is phased under separate permissions, each phase is assessed on its own facts, which can either help or hurt depending on the demolition sequence.
When boroughs also charge their own levy
Nearly every London borough has adopted its own CIL charging schedule, and those rates vary by use and often by geography within the borough. The borough calculates and issues notices for both levies, so you receive one liability notice covering the Mayoral charge and the borough charge separately identified.
Instalment policies differ. The Mayor sets the payment periods for the Mayoral charge, and the borough sets its own for the borough charge, which means a single development can face two payment timetables. Read both before you build the cash flow, because CIL is payable on commencement and cannot be deferred to first sale.
For schemes where the combined levy burden and affordable housing provision are in tension, the evidence goes into a Viability Assessment prepared to the RICS guidance on financial viability in planning, with the levy treated as a fixed cost rather than a negotiable contribution. Levy rates are not negotiable, which is why they are usually modelled first and the affordable housing offer tested against what is left.
Liability notices, commencement notices and payment
The procedure is mechanical and unforgiving. Miss a step and you lose the right to pay by instalments, and surcharges follow.
- Submit an Assumption of Liability form before development starts, naming the party who will pay.
- Receive the liability notice from the borough, which states the chargeable amount for each levy and the payment schedule.
- Submit any relief or exemption claim and receive a decision before commencement, because relief claimed after the start of works is lost.
- Submit a Commencement Notice to the borough before development starts, stating the intended commencement date.
- Receive the demand notice and pay by the stated dates.
The Commencement Notice is the step that trips up experienced developers. Starting on site without serving it removes the instalment entitlement, makes the full amount payable immediately and attracts a surcharge. Site clearance and demolition can count as a material operation, so serve the notice before anyone moves a machine onto the site.
Exemptions and relief
The main reliefs apply to the Mayoral charge as they do to any CIL: social housing relief, charitable relief, the self-build exemption, and the exemptions for residential annexes and extensions. Minor development below 100 m² of new floorspace is exempt where it does not create a new dwelling.
Each relief has its own form, its own evidence requirements and, for self-build, a clawback period during which the dwelling must remain the applicant's principal residence. Social housing relief is claimed on the qualifying units and requires the tenure to be documented, which is normally handled alongside the Affordable Housing Statement submitted with the application.
Relief is not automatic and it is not retrospective. A claim has to be granted before commencement, and a claim made after works start is simply too late.
Budgeting for both levies
Model the levy from the drawings rather than from the unit count. Two schemes with the same number of homes can differ sharply in gross internal area once circulation, plant and basements are counted, and the levy follows the area.
Build the appraisal in this order: measure GIA by use, establish and evidence the deduction for existing lawful floorspace, apply the Mayoral rate for the band and, where relevant, the higher commercial rate for the zone, then apply the borough rate, then apply indexation for the expected year of permission. Hold a contingency for the deduction failing, because the six-month lawful use test is the item most often disputed.
Check the current Mayoral charging schedule and the borough's own schedule at the point you fix the appraisal, since both are revised and the levy is indexed annually. To scope the wider evidence base for a London scheme, enter the postcode on PlanScope or work through the report categories before you commit to a submission date.
This is general guidance, not legal advice. Levy calculations turn on the facts of each site, so check the position with the borough's CIL officer 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.
Frequently asked questions
Is Mayoral CIL charged in addition to borough CIL
Yes. The Mayor of London charges across all London boroughs and the City of London, and almost every borough also has its own adopted charging schedule. The borough collects both and identifies them separately on the liability notice. Paying one does not reduce the other, and neither displaces a section 106 obligation.
How is chargeable floorspace measured
On net additional gross internal area. You measure the GIA of the new development by use, then deduct the GIA of existing buildings that qualify, which means buildings in lawful use for a continuous six months within the three years before permission first permits the development. Mezzanines, plant rooms and basements all count towards GIA.
What happens if I start work without a commencement notice
You lose the right to pay by instalments, the whole chargeable amount becomes payable immediately and a surcharge is applied. Demolition and site clearance can amount to a material operation, so the notice needs to be served before any machine arrives. The notice goes to the collecting authority, which is the borough.
Can I claim relief after planning permission is granted
You can claim after permission but you must have a decision on the claim before development starts. Relief claimed after works start is lost, with no discretion to reinstate it. Social housing relief, charitable relief, the self-build exemption and the annexe and extension exemptions each have their own form and evidence requirements.
Why does a long-vacant building increase my levy
Because the deduction for existing floorspace depends on lawful use for six continuous months in the preceding three years. A building empty beyond that window cannot be netted off, so its floorspace is charged as if the site were vacant land. Gather rates records, tenancy documents and utility accounts early to evidence occupation.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.