N.Y. Comp. Codes R. & Regs. tit. 20, § 16-2.8 – Definition of bona fide office.

(a) A bona fide office is an office at which the taxpayer is carrying on its business in a regular and systematic manner and which is continuously maintained, occupied and used by one or more employees of the taxpayer. For a taxpayer to be carrying on its business in a regular and systematic manner, its business must be conducted through its own employees who are regularly in attendance at such office during normal business hours. The occasional consummation of a transaction does not constitute the carrying on of a business in a regular and systematic manner.
(b) In determining whether the taxpayer has a bona fide office, consideration is given to such things as:
1. (1) the nature and location of the business;
2. (2) the nature of the activity engaged in at each location; and
3. (3) the regularity, continuity and permanency of the activity at each location.