Audit Department

Operating like the Internal Affairs unit in a police department, the audit department is a division within a company's financial hierarchy tasked with making sure that the firm's financial results truly match what's going on. The department enacts procedures to make sure accounting gets done according to proper procedures. It also conducts periodic audits to make sure everything remains above board.
The audit department is separate from the independent auditors who periodically come in to look over a company's financial results. If the audit department is the PD's Internal Affairs division, then the outside auditors are the city councilmen who sometimes go with a couple officers on a ride along.