The salary account is drained at a designated time every week, for salary. Keeping this full is one of the most important parts of the game. To do this click on the staff link on the left hand side of your screen. Then click on the salary tab in the middle of the screen and deposit the amount you wish. Here you can also adjust which day and at what time the money is deposited. Failing to have the right amount of money in your account at the time salaries are paid out will result in a loss to company value and a very dissatisfied staff.