“…Although we expect focus, expertise, and autonomy of IAFs to have an influence on the level of co-sourcing for internal audit activities, the associations we defined in our hypotheses may suffer changes depending on whether the IAF is voluntary or mandatory for specific organizations in a given institutional context. Though there is a wide range of empirical literature about the substitution or complementary effect between internal and external audit activities (Carey et al, 2000;Elliott & Korpi, 1978;Felix, Gramling, & Maletta, 2001;Hay, Knechel, & Ling, 2008;Hay, Knechel, & Wong, 2006;Ho & Hutchinson, 2010;Mohamed et al, 2012;Prawitt, Sharp, & Wood, 2011;Stein, Simunic, & O'Keefe, 1994), there are no studies, to our knowledge, examining the relationship between IAF characteristics and co-sourcing, depending on whether the IAF is voluntary or mandatory.…”