(b) Examination of books and witnesses.-- The administrator for the purpose of ascertaining the correctness of any return, or for the purpose of making an estimate of taxable income of any person, shall have power to examine or to cause to have examined, by any agent or representative designated by him for that purpose, any books, papers, records or memoranda bearing upon the matters required to be included in the return, and may require the attendance of the person rendering the return or any officer or employee of such person, or the attendance of any other person having knowledge in the premises, and may take testimony and require proof material for his information, with power to administer oaths to such person or persons.

(c) Abatement authority.-- The administrator, of his own motion, may abate any small unpaid balance of an assessment of income tax, or any liability in respect thereof, if the administrator determines under uniform rules prescribed by him that the administration and collection costs involved would not warrant collection of the amount due. He may also abate, of his own motion, the unpaid portion of the assessment of any tax or any liability in respect thereof, which is excessive in amount, or is assessed after the expiration of the period of limitation properly applicable thereto, or is erroneously or illegally assessed. No claim for abatement under this subdivision shall be filed by a taxpayer.

(d) Special refund authority.-- Where no questions of fact or law are involved and it appears from the records of the administrator that any moneys have been erroneously or illegally collected from any taxpayer or other person, or paid by such taxpayer or other person under a mistake of facts, pursuant to the provisions of this local law, the administrator at any time, without regard to any period of limitations, shall have the power, upon making a record of his reasons therefor in writing, to cause such moneys so paid and being erroneously and illegally held to be refunded.

(e) Cooperation with the United States, other states and the state of New York. Notwithstanding the provisions of section seventy-eight, the administrator may permit the secretary of the treasury of the United States or his delegates, or the proper tax officer of this state or of any other state imposing an income tax upon the incomes of individuals, or the authorized representative of either such officer, to inspect any return filed under this local law, or may furnish to such officer or his authorized representative an abstract of any such return or supply him with information concerning an item contained in any such return, or disclosed by any investigation of tax liability under this local law, but such permission shall be granted or such information furnished to such officer or his representative only if the laws of the United States or of such state, as the case may be, grant substantially similar privileges to the administrator and such information is to be used for tax purposes only; and provided further the administrator may furnish to the commissioner of internal revenue or his authorized representative or to the tax commission of the state of New York or its authorized representative such returns filed under this local law and other tax information as he may consider proper for use in court actions or proceedings under the internal revenue code or the tax law, whether civil or criminal, where a written request therefor has been made to the administrator by the secretary of the treasury of the United States or by such tax commission or by their delegates provided the laws of the United States or the laws of the state of New York grant substantially similar powers to the secretary of the treasury of the United States or his delegates or to such tax commission or its delegates. Where the administrator has so authorized use of returns and other information in such actions or proceedings, officers and employees of the department of finance of the city may testify in such actions or proceedings in respect to such returns or other information.