CIL is based on the chargeable development’s gross internal floor area (GIA) and your local authority’s charging schedule. The calculation considers existing floorspace. indexation and any applicable reliefs or exemptions.
The collecting authority calculates your CIL liability by identifying the relevant floor area, applying the local CIL rate, and accounting for existing floorspace and any reliefs. The final amount becomes payable when development lawfully commences.
Measure gross internal area of new chargeable development.
Remove any existing lawful internal area.
Use your local authority’s CIL charging schedule rate (£/m²).
Apply indexation in line with your LPA’s charging schedule.
Subtract any approved reliefs or exemptions.
Check if the 100sqm threshold applies to your development.
The remaining amount is your CIL liability.
Find your local CIL rate and indexation details. Charging schedules vary by authority.
Learn what counts as GIA and how it is measured for CIL purposes.
Find out what evidence your LPA will need for any existing lawful floorspace.
Explore self-build, annex, extension and other reliefs and the events that can affect them.
Understand how indexation is applied and how CIL rates can change over time.
Talk to our UK planning experts for help with your CIL calculation or forms.
