Prove It Act of 2019 This bill authorizes the Small Business Administration (SBA) to request a review of any federal agency certification that a proposed rule will not have a significant economic impact on a substantial number of small entities. The request must explain why the SBA disagreed with the certification and provide a factual basis for the statement. If it is determined, after agency review and reconsideration, that the proposed rule will have a significant economic impact on a substantial number of small entities, the agency shall then perform an initial regulatory flexibility analysis for the rule. An initial regulatory flexibility analysis is prepared to ensure the agency has considered all reasonable regulatory alternatives that would minimize the rule's economic burdens or increase its benefits for the affected small entities, while achieving the objectives of the rule or statute.