S106 vs CIL: London's Infrastructure Funding Gap
Planning obligations fund schools, parks, and affordable housing. But the system is complex, opaque, and under growing strain as development volumes rise
S106 planning obligations and Community Infrastructure Levy together form the financial backbone of infrastructure delivery in London. The Planning London Datahub now captures obligation data at application level — revealing the scale of commitments, the variation between boroughs, and the persistent tension between viability and public benefit.
How the System Works
Section 106 obligations are negotiated agreements between developers and local planning authorities — binding legal commitments to deliver infrastructure, affordable housing, or financial contributions. Community Infrastructure Levy is a non-negotiable charge levied per square metre of new floor space, set by each borough and the Mayor. Between them, they are supposed to ensure that development pays for its impact. In practice, the interaction between the two systems is complex, the negotiating of S106 is resource-intensive, and the gap between commitment and delivery is poorly monitored.
What the PLD Captures
The Planning London Datahub records obligation data within the application_details.obligation_details field — capturing whether a S106 has been agreed, the CIL liability, whether a viability assessment has been submitted, and appeal status. This is a significant advance on previous data availability, allowing cross-borough comparisons of obligation levels for comparable scheme types and sizes.
“S106 negotiation is one of the most resource-intensive parts of the planning process. Smaller boroughs lack the specialist expertise of central London authorities, and that shows in the outcomes.”
— London Councils, Planning Capacity Review 2024
Borough Variation
The variation in S106 per unit between boroughs is striking. Southwark, Tower Hamlets, and Lambeth — boroughs with significant development activity and well-resourced planning teams — consistently achieve above-average obligations. Smaller Outer London boroughs, managing fewer applications with less specialist capacity, tend to achieve lower per-unit obligations. This is not simply a function of land values — it reflects the capacity and expertise of the negotiating authority.
Key Infrastructure Categories Funded by S106
- 1Affordable housing contributions (on-site or commuted sums)
- 2Education: primary school places, SEN provision
- 3Transport: junction improvements, bus stop upgrades, TfL contributions
- 4Public open space: new parks, play areas, street planting
- 5Healthcare: GP surgery capacity
- 6Community facilities: libraries, sports halls
- 7Employment and skills training
The Uncommenced Problem
A significant proportion of consented S106 obligations are not yet triggered — the development has been consented but not started, so the obligation has not yet crystallised. The PLD data suggests approximately 33% of obligations by value are in this uncommenced category. As market conditions slow development starts, infrastructure delivery is deferred — placing strain on boroughs that have planned for contributions that have not yet arrived.