From the help page:
Budget Information, Player Payroll Budget - This captures your current budget status. The player payroll figure represents the amount that you have allocated to your player payroll +/- any transferred cash from trades. The amount that you may allocate to future seasons is reduced by 80%, 70%, 50% and 50% in order to prevent trashing a franchise for the future. You may not allocate more than this payroll budget for any season.