It shall be the duty of such board of assessors and they are hereby authorized and empowered, to ascertain the amount of all taxes paid by the association, as herein contemplated, as soon as practicable after the payment thereof, and thereupon to fix and determine on the basis aforesaid the sum or sums of money to be paid to the association by each of the owners of such cottages or buildings as his, her, or their just proportion of taxes paid by the association, and shall report to the board of trustees such determination and finding in writing, and the sum or sums of money thus fixed and determined, as shown by said report, shall be final and conclusive upon all parties, and shall constitute an indebtedness and lien as aforesaid payable from the date of filing of such report with the collection fees allowed township treasurers for the collection of taxes. To all taxes unpaid on the first day of March next after their assessment, there shall be added interest and collection fees at the same rate as provided by law for the non-payment of taxes on and after said date.