Section 71. Mailing rules; holidays

--(a)  Timely  mailing.--If any claim,
  statement, notice, petition, or other document (including to the  extent
  authorized  by the administrator, a return or a declaration of estimated
  tax) required to be filed within a prescribed period or on or  before  a
  prescribed  date  under authority of any provision of this local law is,
  after such period or such date, delivered by the United States  mail  to
  the  administrator, bureau, office, officer or person with which or with
  whom such document is required to be  filed,  the  date  of  the  United
  States  postmark  stamped on the envelope shall be deemed to be the date
  of delivery. This subdivision shall apply  only  if  the  postmark  date
  falls  within  the prescribed period or on or before the prescribed date
  for the filing of such document, determined with regard to any extension
  granted for such filing, and only if such document was deposited in  the
  mail,  postage prepaid, properly addressed to the administrator, bureau,
  office, officer or person with  which  or  with  whom  the  document  is
  required  to  be  filed.  If  any  document  is  sent  by  United States
  registered mail, such registration shall be prima  facie  evidence  that
  such  document  was  delivered  to  the  administrator,  bureau, office,
  officer or person to which or to whom addressed. To the extent that  the
  administrator  shall prescribe by regulation, certified mail may be used
  in lieu of registered mail under this section.  This  subdivision  shall
  apply in the case of postmarks not made by the United States Post Office
  only if and to the extent provided by regulations of the administrator.
    (b)  Last known address.--For purposes of this local law, a taxpayer's
  last known address shall be the address given in the last  return  filed
  by  him,  unless  subsequently to the filing of such return the taxpayer
  shall have notified the administrator of a change of address.
    (c) Last day a Saturday, Sunday or legal holiday.--When the  last  day
  prescribed under authority of this local law (including any extension of
  time)  for  performing  any  act  falls  on Saturday, Sunday, or a legal
  holiday in the state of New York, the performance of such act  shall  be
  considered timely if it is performed on the next succeeding day which is
  not a Saturday, Sunday or a legal holiday.