Denham is a lawyer who for over 30 years has specialised in advising on all aspects of tax and trust law (including the laws applying to charities). He has been a principal with major law and accounting firms in New Zealand and Australia and also the principal of his own specialist tax and trust law practices. Denham has published widely on many tax and trust law topics and has considerable experience and success in assisting clients and their advisers in resolving contentious issues and disputes with regulators and other claimants.