Section 16. The register shall, except as herein provided, send by mail to the commissioner of revenue a copy of every inventory and appraisal filed in his court by an executor, administrator or trustee, within thirty days after the filing of the same. The register shall also, within the same period, send by mail to said commissioner a copy of the will of the decedent, if such has been allowed by the probate court. The register shall also furnish such copies of papers in his office as the commissioner shall require, and shall furnish information as to the records and files in his office in such form as the commissioner may require. A refusal or neglect by the register so to send a copy of such inventory and appraisal or to furnish such copies or information shall be a breach of his official bond; but the commissioner may excuse him from sending copies of inventories and of wills of estates no part of which, in his judgment, appears to be subject to a tax under chapter sixty-five or chapter sixty-five C. If an executor, administrator or trustee fails to file said inventory and appraisal within three months from the date of his appointment, the register shall within thirty days after the expiration thereof notify the commissioner of such failure.