How CIL is calculated
CIL is charged on the net additional gross internal area (GIA) of the new dwelling at the local-authority published rate (£/sqm), multiplied by the BCIS All-in TPI indexation factor since the charging schedule adoption date[MHCLG CIL]. Charge rates vary wildly: outer London £40-£250/sqm of net additional GIA; many rural authorities £0; Mayoral CIL £25-£150/sqm in London on top of borough CIL.
The self-build exemption
Form 7 Part 1 (claim) and Part 2 (commencement notice) wipe the entire CIL charge for owner-occupier self-builds. The claimant must own and occupy the dwelling as a primary residence for at least 3 years after completion. Form 7 must be submitted and acknowledged before commencement of works; missing the procedural sequence is fatal.
Section 106 on single dwellings
Section 106 planning obligations are usually negotiated on major developments (10+ dwellings or 1,000 sqm+). On a single replacement dwelling S106 is rare; occasional triggers include affordable-housing contributions in some Outer London boroughs (under £30k typical) or biodiversity offsets on AONB plots.
Process to claim the exemption
Step 1 (pre-application): note the intent in the planning Design and Access Statement. Step 2 (post-permission): submit Form 7 Part 1 to the collecting authority and wait for acknowledgement. Step 3 (pre-start): submit Form 6 (Commencement Notice) before any works begin on site, including demolition. Step 4 (post-build): submit Form 7 Part 2. Skip any step and the exemption is lost.