S106 vs CIL: A Planning Officer's Guide to Both Systems

Section 106 agreements and CIL both fund infrastructure from development — but they work differently, apply differently, and need different monitoring processes. If you manage both at a smaller council, you're probably tracking them in separate spreadsheets with different structures. This creates reporting headaches, especially come IFS time.

This guide covers how the two systems interact from a monitoring perspective — what planning officers need to track, where they overlap, and where they diverge.

This covers England only. This is general guidance, not legal advice.

The Core Difference

S106 (Section 106 agreements) are negotiated, site-specific obligations under Section 106 of the Town and Country Planning Act 1990. Each agreement is bespoke. The developer commits to delivering or funding specific infrastructure tied to the impact of their development.

CIL (Community Infrastructure Levy) is a fixed-rate charge set by the council's charging schedule, applied to qualifying development based on floor area. It funds general infrastructure — the council decides where to spend it (subject to the reporting requirements in Schedule 2 of the CIL Regulations).

	S106	CIL
Set by	Negotiation per application	Published charging schedule
Applies to	Any development with planning impact	Qualifying development above thresholds
Funds	Specific obligations (education, highways, affordable housing)	General infrastructure (council allocates)
Legal basis	TCPA 1990, s.106	CIL Regulations 2010
Pooling limit	Removed (was limited to 5 agreements pre-2019)	No pooling limit
Spend restrictions	Must match purpose in agreement	Must fund infrastructure types on the council's Infrastructure List
Neighbourhood share	No statutory requirement	15% to parish (25% if neighbourhood plan adopted)
Clawback	Yes — spend-by deadlines in agreement	No — once collected, no time limit on spend

When Both Apply to the Same Development

On a qualifying development, both CIL and S106 can apply simultaneously. The developer pays CIL based on the charging schedule and enters an S106 agreement for site-specific obligations that CIL doesn't cover.

The critical rule: S106 cannot duplicate CIL. If your council's Infrastructure List identifies education as a CIL-funded infrastructure type, you generally cannot also seek an S106 education contribution from the same development for the same purpose. However, site-specific mitigation that goes beyond the general CIL provision can still be secured through S106.

In practice, most councils use:

• CIL for general infrastructure categories (strategic transport, community facilities, green infrastructure)
• S106 for site-specific requirements (affordable housing, direct access works, on-site open space, development-specific education provision)

The boundary isn't always clean. Planning officers need to know their council's Infrastructure List and apply it consistently when negotiating S106 terms.

What This Means for Monitoring

Different Data Models

S106 monitoring tracks individual obligations with triggers, financial terms, and spend-by deadlines. Each agreement is different. The data model is obligation-level, nested within agreements.

CIL monitoring tracks a standardised charge through a fixed lifecycle: liability notice → demand notice → payment → allocation → spend. The data model is transaction-level with uniform fields.

Trying to monitor both in a single spreadsheet format creates compromises. S106 needs flexible, obligation-level tracking. CIL needs structured, transaction-level tracking. Most councils end up with two separate systems — which is fine operationally but creates problems at IFS reporting time.

Different Deadlines

S106 contributions have spend-by deadlines defined in each agreement — typically 5–10 years from receipt. Miss the deadline and the developer can reclaim the money.

CIL has no statutory spend-by deadline. Once collected, the council can hold CIL indefinitely (though this raises questions about infrastructure delivery and transparency).

This means your deadline alerting system only needs to cover S106, but your IFS reporting needs to cover both.

Different Financial Tracking

S106 financial contributions are index-linked (usually BCIS or RPI) and the amount varies by agreement. You invoice the indexed amount at the trigger date.

CIL is calculated at the point of planning permission using the published rate, adjusted by the national BCIS index. The amount is fixed once the demand notice is issued.

Both need receipt tracking, but S106 requires more manual calculation at the invoicing stage.

IFS Reporting: Where S106 and CIL Converge

The annual Infrastructure Funding Statement requires separate sections for CIL and S106 — but both appear in the same published document. This is where having two separate monitoring systems creates the most friction:

• Section 2 (CIL Report) requires: receipts, expenditure, admin costs, neighbourhood portion, and retained balance
• Section 3 (S106 Report) requires: agreements entered into, money received, money spent, money retained, and non-monetary contributions delivered

If your CIL data lives in a billing system and your S106 data lives in a spreadsheet, compiling the IFS means extracting data from two places, reconciling it with a third (finance), and assembling it into a single document. This is why the IFS takes days at councils without structured monitoring.

For a step-by-step IFS compilation process, see How to Produce Your Infrastructure Funding Statement in Half the Time. You can also generate a starting template with the free IFS Template Generator.

The Neighbourhood Portion: A CIL-Specific Complication

CIL includes a mandatory neighbourhood portion: 15% of CIL receipts from developments in a parish area must be passed to the parish council (25% if the parish has an adopted neighbourhood plan). This doesn't apply to S106.

For monitoring purposes, you need to:

• Track which developments fall within parish boundaries
• Calculate and pass the neighbourhood portion within the required timeframe
• Report the amount passed in your IFS

Parishes can spend their neighbourhood portion on a wider range of purposes than the council can spend its share — including anything that addresses the demands of development in the area. But they must report on how they've spent it, which creates an additional tracking requirement.

Practical Implications for Planning Teams

If you manage both S106 and CIL:

1. Keep your Infrastructure List current. This is what determines whether an infrastructure type is funded through CIL (general charge) or S106 (site-specific). An outdated list creates double-dipping risks and legal challenges from developers.

2. Track S106 deadlines actively, CIL balances passively. S106 has financial consequences for missed deadlines. CIL does not. Allocate your monitoring effort accordingly.

3. Align your data structures for IFS reporting. Even if you use separate systems for S106 and CIL, standardise the reporting fields so your IFS compilation pulls from consistent data. Use the same infrastructure categories in both systems.

4. Record the relationship between CIL and S106 on each application. When a development pays CIL and has an S106 agreement, note this on both records. This prevents confusion about which contribution funds which infrastructure item.

5. Use the IFS as a data quality check. If your IFS numbers don't reconcile, you have a monitoring problem that extends beyond reporting. Fix the underlying data issue, not just the IFS.

For an overview of S106 monitoring processes, see The Complete Guide to S106 Monitoring for Planning Officers.

Sources

• Town and Country Planning Act 1990, Section 106
• Community Infrastructure Levy Regulations 2010
• Community Infrastructure Levy (Amendment) (England) (No. 2) Regulations 2019
• PAS — Infrastructure Funding Statements
• GOV.UK — Planning Obligations Guidance