N.Y. Comp. Codes R. & Regs. tit. 12, § 472.6 – Transfers of accounts.

(a) An employer who, subsequent to July 1, 1951, acquires the organization, trade or business, in whole or in part, of an employer liable for contributions shall report such fact, in writing, together with the date of acquisition and the name and other identification of the transferring employer. If only a part of the organization, trade or business is transferred, experience rating charges based on benefits paid to former employees of the transferring employer shall be debited to the account of the transferee.
(b) If only a part of the organization, trade or business is transferred, the transfer ring employer's account, including its balance and all other aspects of its experience under the Unemployment Insurance Law, shall be allocated in proportion to the payroll assignable to the transferred part during the last 12 completed calendar quarters prior to the date of transfer except that the allocation shall be made in proportion to the number of employees assignable to the transferred part in the following cases:
1. (1) if the transferred part of the organization, trade or business was not in existence for 12 completed calendar quarters prior to the date of transfer;
2. (2) if the transferring employer and the transferee join in a request to allocate in accordance with the number of employees, and demonstrate that allocation in accordance with payroll would be inequitable.