Pre-LURA 2023 position (still relevant for transitional cases)
Town and Country Planning Act 1990 s171B as originally enacted: (1) 4-year rule for operational development (erection, extension, alteration of buildings; engineering works) — no enforcement action after 4 years from substantial completion; (2) 4-year rule for change of use of any building to use as a single dwellinghouse — measured from change being substantially complete + continuous; (3) 10-year rule for all other breaches — change of use (e.g. C3 to C4 HMO, residential to commercial), breach of planning condition, change to/from any other use class. Immunity is on the act of enforcement — once time-barred, LPA cannot issue enforcement notice. Certificate of Lawfulness of Existing Use or Development (CLEUD) under s191 confirms lawful status — see [[certificate-of-lawfulness-existing-use-london]]. Burden of proof on applicant — must evidence continuous existence/use for required period via dated photos, utility bills, council tax records, sworn affidavits from neighbours.
Post-LURA 2023 single 10-year rule
Levelling-up + Regeneration Act 2023 amended s171B with effect 25 April 2024 (England only — Wales retains 4/10 split). Now: single 10-year time limit for all breaches of planning control in England. Rationale (per government policy): consistency, deters unauthorised development by extending immunity period, gives LPAs more time to enforce against historic breaches. Practical effect: unauthorised extensions, lofts, change-of-use to dwelling that would have become immune at 4 years now require 10 years continuous existence. Doubles the risk window for unauthorised works. Transition (saved provisions): breaches that had already become immune at 4 years before 25 April 2024 retain their immune status — cannot be re-enforced. Breaches not yet immune at 25 April 2024 fall under new 10-year rule. Limited transitional uncertainty: breaches with partial 4-year accrual but not yet immune face new 10-year wait — legal challenges to retrospective application possible but not yet tested. Listed building works remain enforceable indefinitely under s9 Planning (Listed Buildings + Conservation Areas) Act 1990 — no immunity at any time.
