The implementation of the Markets in Financial Instruments Directive will affect the securities markets and investment firms of all EU member states. The measures in the directive are primarily targeted at regulated firms operating in the financial markets, but MiFID will also have an impact on corporates active in the markets as customers of regulated firms. Treasurers do not need to be experts on MiFID, but they do need to be aware of the implications for their companies. With this in mind, the ACT has published a guidance note that goes into the full technical details of MiFID as useful background for the treasurer, in-house lawyer, or company secretary. This summary article explains the specific practical changes that will affect corporates.