In determining the optimal audit interval, the losses that accrue in the absence of auditing must be balanced against the cost of conducting the audit (CJ). More frequent audits imply higher audit costs but lower losses. If the reduction in losses outweighs the higher audit costs, over a specified planning horizon, then more frequent audits are optimal up to the point where the reduction in losses equals the increase in audit costs over a specified planning horizon covering a number of audit intervals.
Following Boritz and Broca,, the total cost for an audit interval t^ is the sum of Lp) plus Cj{t):
TCpJ = Lp) + Cp). (3)