N.Y. Comp. Codes R. & Regs. tit. 4 § 28-3.5
Before absence for personal illness may be charged against donated leave credits, the appointing authority may require such proof of illness as may be satisfactory to it, or may require the employee to be examined, at the expense of the department or agency, by a physician designated by the appointing authority. In the event of failure to submit proof of illness upon request, or in the event that, upon such proof as is submitted or upon the report of medical examination, the appointing authority finds that there is not satisfactory evidence of illness sufficient to justify the employee's absence from the performance of his/her duties, such absence may be considered as unauthorized leave and shall not be charged against donated leave credits. Abuse of leave privileges shall be cause for disciplinary action.
N.Y. Comp. Codes R. & Regs. Tit. 4 § 28-3.5