A corporate action rate is the figure in an event announcement that states how much a holder receives for each unit of the security held. For cash events it is an amount per share or per unit of nominal value, such as a dividend of 0.25 per share or a bond interest payment derived from the coupon rate. For securities events it is an entitlement ratio, such as one new share for every ten held.
Rates are quoted gross and, where tax is deducted at source, net of withholding tax. An event can also carry several rates, one for each option or for different classes of holder, and a rate may be announced in one currency and paid in another. The rate is the main input to the corporate action entitlement calculation, so operations teams confirm it against more than one source and watch for late changes by the issuer.