For appropriation and expenditure purposes, encumbrances represent financial obligations which are chargeable to the current biennium's appropriation and for which a part of that appropriation is reserved. Encumbrances which are established in one biennium to be liquidated in a subsequent biennium shall be limited to the following types of transactions:
(1) A purchase order is issued, but the goods and accompanying invoice were not received and paid during the same biennium;
(2) Goods or services were received, but an invoice has not been received and paid;
(3) Goods or services and an invoice were received, but payment could not be made during the same biennium;
(4) Salaries have been earned and are payable to the employees, but have not been paid as of the end of the biennium as a result of pay periods not being consistent with the end of the biennium, except that higher education institutions may encumber payrolls for the remainder of the summer session which is in progress at the end of the state's biennium if they have been budgeted and appropriated in such manner; and
(5) A written agreement for a grant or award to distribute aid was signed but was not paid during the same biennium.