Must - a specific requirement in the Solicitor's Code of Conduct or legislation. You must comply, unless there are specific exemptions or defences provided for in the code of conduct or relevant legislation.
Should - good practice for most situations in the Law Society's view. If you do not follow this, you must be able to justify to oversight bodies why this is appropriate, either for your practice, or in the particular retainer.
May - a non-exhaustive list of options for meeting your obligations. Which option you choose is determined by the risk profile of the individual practice, client or retainer. You must be able to justify why this was an appropriate option to oversight bodies.
The Law Society also provides a full glossary of other terms used throughout this practice note