The assessors of any town in which property is located, a portion of which has been conveyed since the date of its assessment, shall, upon request of the owner of such portion, place a valuation thereon, and the tax collector shall, upon demand of such owner, compute the amount of the tax due on such portion and accept payment of such amount from such owner, and such portion shall be free from any lien filed against the property of which it was a portion at the time of the assessment and the tax collector shall note the payment of such tax upon the record of any such lien.