Section 4(1): substituted, on 2 September 1996, by section 2(1) of the Heavy Engineering Research Levy Amendment Act 1996 (1996 No 128).
Section 4(4): substituted, on 2 September 1996, by section 2(2) of the Heavy Engineering Research Levy Amendment Act 1996 (1996 No 128).
Section 4(5): inserted, on 28 October 2021, by section 3 of the Secondary Legislation Act 2021 (2021 No 7).