Section 23. The assessors shall annually assess taxes to an amount not less than the aggregate of all amounts appropriated, granted or lawfully expended by their respective towns since the last preceding annual assessment and not provided for therein, of all amounts required by law to be raised by taxation by said towns during said year, of all debt and interest charges matured and maturing during the next fiscal year and not otherwise provided for, of all amounts necessary to satisfy final judgments against said towns, and of all abatements granted on account of the tax assessment of any year in excess of the overlay and not otherwise provided for or any such deficits resulting from section fifty-three E of chapter forty-four; but such assessment shall not include liabilities for the payment of which towns have lawfully voted to contract debts. Any estimate of interest charges attributable to variable interest rates on obligations issued pursuant to section twenty-two A of chapter forty-four shall be subject to the approval of the commissioner. The assessors shall deduct from the amount required to be assessed (a) the amount of all estimated receipts of their respective towns lawfully applicable to the payment of the expenditures of the next fiscal year, excluding sums to be received from the commonwealth or county for highway purposes, other than funds required to be distributed under section eighteen B of chapter fifty-eight, and excluding estimated receipts from loans and taxes, but including estimated receipts from the excise levied under chapter sixty A and receipts estimated by the commissioner under section twenty-five A of chapter fifty-eight, (b) the amount of all appropriations voted from available funds for the purpose of deduction, and (c) the amount of all other appropriations voted from available funds. Deductions made by the assessors under any provision of this section shall not be subject to the approval of the commissioner; provided, however, that deductions made under clause (a) on account of estimated receipts, other than those estimated by the commissioner, shall not exceed the aggregate amount of actual receipts received during the preceding fiscal year from the same sources, except with the written approval of the commissioner; and provided, further, that deductions made under clauses (b) and (c) shall not exceed the sums certified to the assessors and the commissioner by the director of accounts, after such examination of the accounts of the town as he may deem proper, as the amounts of available funds on hand on the preceding July the first with such additional funds as are hereinafter authorized not otherwise appropriated. Said director shall promulgate and from time to time revise rules and regulations for determining the available funds of a city or town in accordance with established accounting practices of said bureau of accounts. This section shall not be construed to require any approval for the use, application, transfer, appropriation or expenditure of any funds or accounts provision for which use, application, transfer, appropriation or expenditure is made under any other general or special law, beyond such approval or approvals as are required by such other general or special law.

In determining the amount of available funds to be deducted under the provisions of clauses (b) and (c), such available funds shall be the amount certified by the director of accounts as available on July the first next preceding the date of the appropriation, reduced by the amount of all intervening appropriations from available funds, and increased by the total of the proceeds from the sale of tax title possessions and the receipts from tax title redemptions, in addition to the real and personal property taxes of prior fiscal years, and such other amounts as the director may authorize, collected between said July first and a date which shall in no event be later than March thirty-first; provided, however, that no increases to the amount of certified available funds shall be allowed unless such increases have received the written approval of the director prior to the appropriation of such amounts. Such amounts of available funds so certified by the director of accounts as available on the July first immediately preceding shall be reported by the town accountant to the board of selectmen, or by the city auditor to the mayor or city manager and to the city council or board of aldermen, and shall be subject to appropriation.

To the extent that appropriations for programs provided for under chapter seventy-one B have been made without taking into account any reimbursement to which the city or town is entitled during the fiscal year under section thirteen of said chapter seventy-one B, the amount of such reimbursement, but not in excess of such appropriations, shall be included with other estimated receipts by the board of assessors of every city or town when compiling the local tax rate under this section. Such board of assessors shall show as an offset when compiling such rate the amount which represents the excess of such reimbursement over such appropriations.

The auditor or similar accounting officer in each city or town shall certify as soon as may be to the board of assessors the total of the proceeds from the sale of tax title possessions and receipts from tax title redemptions, in addition to the total real and personal taxes of prior years collected from July the first of the current fiscal year up to and including March the thirty-first of the same year.

If, prior to June first the assessors of any city except Boston shall not have received from the city clerk a certificate under section fifteen A of chapter forty-one of the appropriations voted for the annual budget for the next fiscal year and if it appears to them, after inquiry of the city clerk, that such appropriations have not been voted, they shall forthwith assess a tax for said year in accordance with the provisions of this section, except that, in determining the amount of the tax to be assessed, there shall be considered as having been appropriated for the annual budget for said year an amount equal to the aggregate appropriations voted for the annual budget for the then current fiscal year.

Notwithstanding the provisions of any general or special law, the provisions of this section, so far as apt, shall apply to fire, water and improvement districts.

No city, town or district tax rate for any fiscal year shall be fixed by the assessors until such rate has been approved by the commissioner, and a rate shall not be approved until the commissioner determines that the deductions under this section and the overlay addition under section twenty-five are in full compliance of law and are reasonable in amount. No city, town or district tax rate for any fiscal year shall be changed after it has been approved by the commissioner and returned to the assessors; provided, however, that the commissioner may approve a revised rate if: (i) there was a material understatement or overstatement in the returned rate due to an unintentional, inadvertent or other good faith omission or error by city, town or district officials in reporting the rate; and (ii) the tax bills for the year have not been sent.