Fund resources are the collective value of the undisbursed balance (by year account), investments held (at par), unfunded contract authority, borrowing authority, funds held outside of the Department of the Treasury, unrealized discount, unamortized premium and discount, and accounts receivable (reimbursements earned, refunds only when collected, and unfilled customer orders). Refer to the Office of Management and Budget Circular No. A-11, Section 20.4, for more detail about budget authority.