N.Y. Comp. Codes R. & Regs. tit. 9, § 6217.7 – Processing voters who move between counties.

(a) NYSVoter shall identify as voters that have moved between counties those voters who have stated on their application that the last year they voted, or were registered to vote, was in a county other than where they are applying to register to vote and the voter provided the previous address at which they were registered.
(b) NYSVoter shall notify affected counties of an apparent duplicate voter record, and thus a possible move between counties based upon a match of an applicant's name and date of birth.
(c) NYSVoter shall provide the capability for the county to verify that a voter has moved between counties based upon a match of the applicant's signature and either the New York State Department of Motor Vehicles driver license or non-driver number or last four digits of the voter's social security number or matching of the previous address of the voter.
(d) When a Board of Elections receives notice that a voter on the statewide list has moved to an address in such Board of Elections’ county or city, the Board of Elections shall transfer the voter to the new address and send a transfer notice as provided for in Election Law, section 5-208(1)(5).
(e) NYSVoter shall notify the "from county" if a voter has moved their voter registration between the counties. After determining that the voter has moved, the "to county" will effectuate the transfer and substitute the NYSVoter assigned unique identifier with such unique identifier of the "from county". The NYSVoter system shall allow all information associated with the registration to be viewed by the "to" county.
(f) NYSVoter shall notify the "from county" if a voter has moved their voter registration between counties. In such cases, the "from county," upon determining that such records are for the same voter, shall cancel the voter record in their county and provide the required cancellation notice to the voter pursuant to Election Law, section 5-402. In such cases where the "from county" is unable to determine that the proposed duplicate records are from the same voter, after providing the required notice to the voter, the "from county" shall place such voter in inactive status.
(g) NYSVoter shall facilitate the move process if the "to county" has been informed of the registrant's "from county" on the voter registration form or from the registrant.
(h) The moving of voters from one county to another may occur as a result of a new voter registration form being processed or by any mechanism provided for in Election Law section 5-208.
(i) Applicable to transfers.
Any Board of Elections which receives information that a voter has moved to an address in another county in New York State which would have permitted such "from county" board to transfer the voter registration address within the county if the address indicated was an in-county change of address, shall send a copy of the address transfer information, including a voter registration number to the "to county" Board of Elections where the voter has moved. The "to county" shall, using such voter’s information contained in NYSVoter, including enrollment and signature exemplar, along with the new address information, place the voter at the new address pursuant to Election Law section 5-208 and provide notice to the voter in the manner provided in this section. When the "from county" forwards transfer information to another county Board of Elections for further processing, the "from county" shall send a confirmation notice in a form approved by the State board to the prior address of such voter in the "from county." Further list maintenance steps as required by this Part shall be undertaken upon notification by NYSVoter that the voter is registered at an address in another county in New York or upon notification received from the voter.
(j) If such registration or change of address information effectuating such transfer also reflects a change of enrollment as evidenced by the NYSVoter record, the "to county" Board of Elections shall also treat such as an application for a change of enrollment pursuant to Election Law section 5-304.