Certain developments may be exempt from the CIL, qualify for relief, or be eligible for phase credits where development is carried out in stages. Where a Liability Notice has been issued, any exemption or relief must be formally claimed - usually before development commences - as relief is generally unavailable once works have started.

In assessing eligibility, the local authority must consider any public subsidy received in the previous three years. Exemptions may apply to minor development, self-build housing, and residential annexes or extensions. If a development benefiting from an exemption or relief is later altered, a further claim may be required.

Relief may be available for charitable development, social housing, or in exceptional circumstances, with some reliefs being mandatory and others discretionary. For phased development, CIL is typically calculated per phase, with credits applied where liabilities change between phases.

All exemptions, reliefs and phase credits are subject to strict procedural requirements, and failure to comply may result in the full levy becoming payable.