The leading case on the test for "dishonesty" is Ivey v Genting Casinos AC 391.
“Dishonesty” is an essential element in most offences under the 19 Acts but it is not comprehensively defined in either. Those offences are the subject of separate guidance which can be accessed here and here. It does not deal with offences under the Fraud Act 2006 or the Proceeds of Crime Act 2002. This Guidance deals with the most common offences under the Theft Act 1968 ("the 1968 Act") and the Theft Act 1978 ("the 1978 Act").
There is further guidance on these topics in Blackstone's Criminal Practice Section B4 "Theft, Handling Stolen Goods and Related Offences." Introduction Whilst theft and the other offences under the 19 Acts may appear straightforward and often are straightforward on the facts of a specific case, there are also potential pitfalls which prosecutors need to be aware of when deciding, for instance, what is the correct charge for someone who has dishonestly cashed a cheque.
The purpose of this Legal Guidance is to assist prosecutors in selecting the right charge in accordance with the Code for Crown Prosecutors when reviewing cases which may fall under either the Theft Act 1968 ("the 1968 Act") or the Theft Act 1978 ("the 1978 Act"). Payment on the spot required or expected.Undertaking/assisting in the retention, removal, disposal or realisation of stolen goods or arranging to do so.Otherwise than in the course of stealing.Without the consent of the owner or other lawful authority.Theft: Robbery, Burglary, Handling and Going Equipped.