This excerpt taken from the CSCO DEF 14A filed Sep 23, 2009.
Each participant may authorize periodic payroll deductions in any multiple of 1% of his or her eligible earnings each offering period (up to a maximum of 10% of eligible earnings each offering period). The accumulated deductions will automatically be applied on each purchase date to the purchase of whole shares of common stock at the purchase price in effect for that purchase date. Participants are permitted to make other approved contributions prior to a purchase date in certain non-U.S. jurisdictions where payroll deductions are prohibited by law. For purposes of the Purchase Plan, eligible earnings generally include base salary, bonuses, commissions and overtime pay, provided that the definition of eligible earnings differs in the IESPP.