N.Y. Comp. Codes R. & Regs. tit. 9, § 4081.2
In order to qualify for registration as a New York-bred, a thoroughbred horse must have been foaled in New York State and:
(a) For resident mares.
In order to qualify for registration as a New York-bred, the foal of a resident mare must have been foaled in New York State and the dam of such foal must have been continuously in residence in New York State from the date of conception in New York State or within 120 days after her last cover in the year of conception occurring outside New York State until foaling.
(b) For non-resident mares.
In order to qualify for registration as a New York-bred, the foal of a non-resident mare must have been foaled in New York State, and the dam of such horse must have been bred back in New York State to a registered New York stallion in the year of foaling and must have remained in New York State for a minimum of 90 consecutive days after arrival. If the dam of such foal is bred to a stallion outside of New York State in the year of foaling, the foal of the new resident mare shall not be eligible for registration as a New York-bred.
(c) Mares from public auction.
Effective for public auction sales occurring on or after November 1, 2019, a non-resident mare that is purchased in foal through public auction will be deemed to be a resident mare for all purposes if each of the following conditions is satisfied: