Section 18. The commission so established shall not later than fifty days from the issuance of a certificate of organization by the state secretary prepare an estimate of the amount of money required to pay the costs and expenses of the district for the current fiscal year and, in the case of the district being dissolved for the purpose of organizing a district in accordance with section nine, the costs and expenses of said predecessor district incurred during the current fiscal year for which funds are not otherwise available, and, after first subtracting from such estimate of costs the amount of unexpended monies in the custody of the commission which were previously received by the predecessor district from member cities and towns for the expenses of the current fiscal year, the commission shall apportion, assess and certify for payment the amount so determined in accordance with this section.

Each city and town treasurer shall not later than thirty days from the receipt of said certification pay the amount so apportioned and certified from any monies available in the treasury of each such city or town, and the board of assessors of each such city or town shall include said amount in the assessment for the annual tax levy if such tax levy has not been assessed, but otherwise shall include said amount in the next annual tax levy in addition to any amount to be raised for the purposes of the commission for the next fiscal year in accordance with this section.

The commission shall operate on a fiscal year beginning with July first and ending with the following June thirtieth. The commission shall, annually in the month of October, estimate the amount of money required to be assessed upon the cities and towns in the district necessary to pay the cost and expenses of the district for the following fiscal year. The amount so determined for the district shall not exceed a sum equivalent to thirty cents per capita of the population of the district or fifty thousand dollars, whichever is the greatest amount; and said amount shall be apportioned and assessed upon each city and town in the district in the proportion which the population of each such city or town bears to the total population of the district, provided, however, that the population of the district and of each city and town shall be the population as determined by the most recent national decennial census exclusive of the population in any county, state or federal institutions otherwise included in such census. The amounts so apportioned for each city and town shall, prior to December thirty-first of each year, be certified by the district treasurer to the treasurers of each city and town within the district. Each city and town treasurer shall pay the amount so apportioned by the district treasurer not later than July tenth of the fiscal year for which the apportionment is made, and shall make such payment from any monies available in the treasury of each such city or town. The district treasurer shall submit a duplicate copy of the aforementioned certification to the board of assessors of each city and town, and each such board of assessors shall include said amounts in the assessment for the annual tax levy according to the procedures specified in section twenty-one of chapter fifty-nine; provided, however, that if the annual tax levy is determined by any such board of assessors prior to receiving a copy of said certification, the board of assessors shall include as money to be raised in the tax levy an amount equal to twenty cents per capita of the population of the city or town as determined aforesaid, and, if said amount is less than the amount actually certified by the district treasurer, the difference shall be included as money to be raised in the next annual tax levy.

Payments for the expenses of the district shall be made by the treasurer or assistant treasurer only upon a warrant for such payment approved by a majority of the commission or, if so delegated, by a majority of the executive committee or by a majority of such other committee as the commission may delegate by its by-laws to exercise such approval.

Said regional planning and economic development district may accumulate reserve funds for, but not limited to, the purposes of funding the purchase and replacement of capital equipment and participating in state and federal programs, provided, that such accumulated reserve funds may not exceed the estimated proportion of the district commission's costs and expenses to be paid by the member cities and towns during the next fiscal year.

The director of accounts in the department of corporations and taxation shall annually cause an audit to be made of the accounts of the commission. A report thereon shall be made to the chairman of the commission and a copy thereof shall be sent in a city having a city manager to said city manager and in all other cities to the mayor, the board of selectmen of each town and to each planning board in the district.