The Director shall bear the burden of proving the existence of a violation, and the time period for which the violation occurred. To prove a violation, the Director must establish:

That the person against whom the penalty is assessed is an operator, or is the president, secretary, or treasurer of an operator, if such operator is a corporation.

That the operator violated section 423 of the Act and § 726.4. The filing of a complaint shall be considered prima facie evidence that the Director has searched the records maintained by OWCP and has determined that the operator was not authorized to self-insure its liability under the Act for the time period in question, and that no insurance carrier reported coverage of the operator for the time period in question.

The Director need not produce further evidence in support of his burden of proof with respect to the issues set forth in paragraph (a) if no party contested them pursuant to § 726.307(b)(3).

The Director shall bear the burden of proving the size of the operator as required by § 726.302, except that if the Director has requested the operator to supply information with respect to its size under § 726.303 and the operator has not fully complied with that request, it shall be presumed that the operator has more than 100 employees engaged in coal mine employment. The person or persons liable for the assessment shall thereafter bear the burden of proving the actual number of employees engaged in coal mine employment.

The Director shall bear the burden of proving the operator's receipt of the notification required by § 726.303, the operator's prior notice of the applicability of the Black Lung Benefits Act to its operations, and the existence of any previous assessment against the operator, the operator's principals, or the operator's officers.

The person or persons liable for an assessment shall bear the burden of proving the applicability of the mitigating factors listed in § 726.302(d).