After the Board shall complete its review of the assessment roll, a majority of the members shall endorse thereon and sign a statement to the effect that the same is the assessment roll of the City the year in which it has been prepared. The omission of such endorsement shall not affect the validity of such roll. Upon the completion of said roll and from and after midnight following the last day for meeting of the Board of Review, the same shall be the assessment roll of the City for county, school and city taxes and for any other taxes on real and personal property that may be authorized by law and shall be conclusively presumed by all courts and tribunals to be valid and shall not be set aside except for causes set forth in the general laws of the State.