The municipal authorities of each municipality shall cause an audit of the municipality's accounts to be made by a recognized independent and qualified accountant as expeditiously as possible following the close of the fiscal year for such municipality and to cover all financial transactions and affairs of the municipality for such preceding fiscal year. Such audit shall be made on a cash or accrual method at the discretion of the municipality. Such audit shall be completed and the annual audit report made by such accountant shall be submitted within six months after the close of the fiscal year in any event, unless an extension of time shall be granted by a written resolution adopted by the municipal authorities. A village may request a waiver of the audit requirement subject to the requirements of subdivision (4) of section 84-304. If a municipality other than a village owns or operates any type of public utility or other enterprise which substantially generates its own revenue, that phase of the affairs of such municipality shall be audited separately from the other functions of such municipality and the result shall appear separately in the annual audit report made by the accountant to the municipality and such audit shall be on an accrual basis and shall contain statements and materials which conform to generally accepted accounting principles. Any municipality, other than a village, operating its utilities through a board of public works may provide for an entirely separate audit, on an accrual basis, of such operations and report and by a different accountant than the one making the general audit. A village which is required to conduct an audit under subdivision (4) of section 84-304 and which owns or operates any type of public utility or other enterprise which substantially generates its own revenue shall have that phase of the village's affairs reported separately from the other functions of such village, the result of the audit shall appear separately in the annual audit report made by the accountant to the village, and the audit shall be on a cash or accrual basis at the discretion of the village.