Who runs the senate when the president of the senate is absent

In a response to public outcry over the internal revenue service's (irs) extent and abuse of power, the federal government has decided to disband the irs in favor of creating a new administrative agency to oversee taxation. as a business owner, what steps might you be able to take to ensure there are control's and limits to the agency's power? how does this compare with the controls available to branches of the government?