Different companies have different rules and regulations for their employee share purchase plan or ESPP. Usually companies offer an ESPP window once a year. All employees interested in employee share purchase plan need to update the company and their desired monthly contribution before the ESPP window commences. Till the window period is open, the monthly salary of the employee is deducted as per his selected contribution. At the end of the window period, the employee can purchase stocks of the company using the money accumulated. Various companies have distinct ways to reach to a stock price for the share and offer a discount on that price for the employer.