The definition of ‘research and development’ is based broadly on generally accepted accounting practice, but subject to certain statutory provisions that can override such practice. For capital allowance purposes, CAA 2001, Sch. 1, Pt. 2 (which contains ‘defined expressions’) has since April 2007 pointed to CAA 2001, s. 437. One effect of this is that the capital allowances definition of research and development includes oil and gas exploration and appraisal (s. 437(2)(b)).