N.Y. Comp. Codes R. & Regs. tit. 9, § 6217.8 – Processing duplicate voters.

(a) NYSVoter shall identify possible duplicate voter registrations as needed by the county board based upon a match of an applicant's first name, last name, and date of birth.
(b) NYSVoter shall identify possible duplicate voter registrations in near real time at or near the time of data entry for all registration application transactions based upon a match of an applicant's first three letters of the first name and the first five letters of the last name, date of birth, and, if available, the unique identification number, or 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. An image of the potential duplicate voter's signature shall be made available to the county boards for comparison.
(c) NYSVoter shall notify the counties with matching records if voters are potential duplicate registrations between counties. The notification shall include pertinent information regarding the voter.
(d) If the information received by the Board of Elections through NYSVoter indicates that a voter is currently registered to vote more than once, the local Board of Elections containing the registration record of the earlier dated registration record, the "from county", shall send such voter the confirmation notice prescribed by section 5-712 of the Election Law and place such voter on inactive status pursuant to section 5-213 of the Election Law.
(e) After determining that the voter is a duplicate, the "to county" will activate a new record.
(f) After determining that the voter is a duplicate, the "to county" will substitute the unique identifier with the unique identifier from the "from county".
(g) Effective date.
Effective immediately except that subdivisions (b) and (f) of this section shall become effective on July 1, 2007.