Depositions for use at a hearing may, with the written approval of the Administrative Law Judge, be taken either by the Director of Practice or the respondent or their duly authorized representatives. Depositions may be taken upon oral or written interrogatories, upon not less than 10 days’ written notice to the other party before any officer duly authorized to administer an oath for general purposes or before an officer or employee of the Internal Revenue Service who is authorized to administer an oath in internal revenue matters. Such notice shall state the names of the witnesses and the time and place where the depositions are to be taken. The requirement of 10 days’ notice may be waived by the parties in writing, and depositions may then be taken from the persons and at the times and places mutually agreed to by the parties. When a deposition is taken upon written interrogatories, any cross-examination shall be upon written interrogatories. Copies of such written interrogatories shall be served upon the other party with the notice, and copies of any written cross-interrogation shall be mailed or delivered to the opposing party at least 5 days before the date of taking the depositions, unless the parties mutually agree otherwise. A party upon whose behalf a deposition is taken must file it with the Administrative Law Judge and serve one copy upon the opposing party. Expenses in the reporting of depositions shall be borne by the party at whose instance the deposition is taken.