the purchaser and did not have reasonable cause to believe that the certificate was improperly provided by the purchaser with respect to such purchase (within the meaning of section 103), then the burden of production of documents and records relating to that exemption shall rest with the purchaser and not with the seller. 506. Attorneys’ and accountancy fees In all disputes concerning taxes imposed by this subtitle, the person engaged in a dispute with the sales tax administering authority or the Secretary, as the case may be, shall be entitled to reasonable attorneys’ fees, accountancy fees, and other reasonable professional fees incurred in direct relation to the dispute unless the sales tax administering authority or the Secretary establishes that its position was substantially justified. 507. Summons, examinations, audits, etc (a) Summons Persons are subject to administrative summons by the sales tax administering authority for records, documents, and testimony required by the sales tax administering authority to accurately determine liability for tax under this subtitle. A summons shall be served by the sales tax administering authority by an attested copy delivered in hand to the person to whom it is directed or left at his last known address. The summons shall describe with reasonable certainty what is sought. (b) Examinations and Audits The sales tax administering authority has the authority to conduct at a reasonable time and place examinations and audits of persons who are or may be liable to collect and remit tax imposed by this subtitle and to examine the books, papers, records, or other data of such persons which may be relevant or material to the determination of tax due. (c) Limitation on Authority in Case of Referral No administrative summons may be issued by the sales tax administering authority and no action be commenced to enforce an administrative summons with respect to any person if a Justice Department referral or referral to a State Attorney General’s Office is in effect with respect to