Corporate actions have been sidelined for too long and deserve to be treated with more respect. No type of investment security can be fully understood without knowledge of its corporate actions. They have implications for the sustainability of an investment's performance but repeatedly more beguiling investment preoccupations put them into the shade.Together with bank clearing and exchange settlement systems, the administration of corporate actions is one of the key co-operative functions tying our highly competitive global finance industry together. In the financial markets of the developed world the efficiency and "risklessness" of corporate actions processing is entirely taken for granted. Yet the volume of complex corporate actions and a common sense estimate of the likelihood of mistakes occurring suggest that industry practitioners and investing clients may be deluding themselves.If knowledge of corporate actions brings us to fully understand the securities they relate to, some familiarity with corporate actions processing is important in gaining an insight into the workings of the securities industry as a system. With the exceptions of accountancy and financial regulation, no other activity involves as many kinds of investment industry participant as corporate actions processing.