ยง  9-112.  Canvass ballots; validity of ballot. 1. The whole ballot is
  void if the voter (a) does any act  extrinsic  to  the  ballot  such  as
  enclosing any paper or other article in the folded ballot or (b) defaces
  or  tears  the  ballot  except that a ballot card which is in perforated
  sections shall not be void because it has been separated  into  sections
  or  (c)  makes  any  erasure thereon or (d) makes any mark thereon other
  than a cross X mark or a check V mark in a voting square, or filling  in
  the  voting  square,  or (e) writes, other than in the space provided, a
  name for the purpose of voting; except that an erasure or a  mark  other
  than  a  valid  mark  made  in a voting square shall not make the ballot
  void, but shall render it blank as to  the  office,  party  position  or
  ballot  proposal in connection with which it is made. No ballot shall be
  declared void or partially blank because a mark thereon is irregular  in
  form.  The  term "voting square" shall include the voting space provided
  for a voter to mark his or her vote for a candidate or ballot proposal.
2. A cross X mark or a check V mark, made by the voter,  in  a  voting
  square at the left of a candidate's name, or the voter's filling in such
  voting square, shall be counted as a vote for such candidate.
3. A vote shall be counted for a person whose name is written in under
  the title of an office or party position only if such name is written by
  the voter upon the ballot in the proper space provided therefor and only
  if  such name is not printed under the title of such office or position.
  A voting mark before or after such written in name shall not  invalidate
  the vote.
4.  If,  in  the  case of a candidate whose name appears on the ballot
  more than once for the same office, the voter shall make a cross X  mark
  or  a  check  V  mark  in  each of two or more voting squares before the
  candidate's name, or fill in two or more such voting  squares  only  the
  first  vote  shall  be counted for such candidate. If such vote was cast
  for the office of governor, such vote shall not be recorded in the tally
  sheet or returns in a separate place on the tally sheet as  a  vote  not
  for any particular party or independent body.
5.  If  a  voter  makes  a  cross X mark or a check V mark in a voting
  square following the word "Yes"  or  the  word  "No",  before  a  ballot
  proposal,  or  fills  in  such square, such mark shall be counted in the
  affirmative or negative, as so indicated.
6. If the voter marks more names than there are persons to be  elected
  or  nominated  for an office, or elected to a party position, or makes a
  mark in a place or manner not herein provided for, or if for any  reason
  it  is  impossible  to  determine  the  voter's choice of a candidate or
  candidates for an office or party position or his or  her  vote  upon  a
  ballot proposal, his or her vote shall not be counted for such office or
  position  or  upon the ballot proposal, but shall be returned as a blank
  vote thereon.
Structure New York Laws
Article 9 - Canvass of Results
Title 1 - Canvass at Polling Places
9-102 - Canvass; General Provisions For.
9-106 - Official Ballots; Accounting for Number Used.
9-108 - Canvass; Ballots, Verifying Number Cast.
9-110 - Canvass; Election Day Paper Ballots That Have Not Been Scanned; Method Of.
9-112 - Canvass Ballots; Validity of Ballot.
9-114 - Counting Ballots; Objections To.
9-116 - Tallying Ballots; Generally.
9-120 - Returns of Canvass; Generally.
9-122 - Proclamation of Result.