N.C. Gen. Stat. § 159-72
A unit of local government may issue funding and refunding bonds under this Article for the purposes listed in G.S. 159-48(a)(4), (5), (6), or (7). Funding bonds may be issued if the debt, judgment, or other obligation to be paid is payable at the time of the passage of the bond order or within one year thereafter. Refunding bonds may be issued at any time prior to the final maturity of the debt or obligation to be refunded. The proceeds from the sale of any refunding bonds shall be applied only as follows: either (i) to the immediate payment and retirement of the obligations being refunded or (ii) if not required for the immediate payment of the obligations being refunded such proceeds shall be deposited in trust to provide for the payment and retirement of the obligations being refunded, and to pay any expenses incurred in connection with such refunding, but provision may be made for the pledging and disposition of any amounts in excess of the amounts required for such purposes, including, without limitation, provision for the pledging of any such excess to the payment of the principal of and interest on any issue or series of refunding bonds issued pursuant to G.S. 159-78. Money in any such trust fund may be invested in (i) direct obligations of the United States government, or (ii) obligations the principal of and interest on which are guaranteed by the United States government, or (iii) to the extent then permitted by law in obligations of any agency or instrumentality of the United States government, or (iv) in certificates of deposit issued by a bank or trust company located in the State of North Carolina if such certificates shall be secured by a pledge of any of said obligations described in (i), (ii), or (iii) above having an aggregate market value, exclusive of accrued interest, equal at least to the principal amount of the certificates so secured. Nothing herein shall be construed as a limitation on the duration of any deposit in trust for the retirement of obligations being refunded but which shall not have matured and which shall not be presently redeemable or, if presently redeemable, shall not have been called for redemption.
The principal amount of refunding bonds issued pursuant to this section, together with the principal amount of refunding bonds, if any, issued under G.S. 159-78 in conjunction with refunding bonds issued pursuant to this section, shall not exceed the amount set forth in G.S. 159-78.
Except as expressly modified in this Part, funding and refunding bonds issued under the provisions of this Part shall be subject to the limitations and procedures set out in Parts 1 and 2 of this Article.
N.C. Gen. Stat. § 159-72