“…To date, other research hypotheses have appeared in the literature on audit fees, such as audit fees inversely depend on the time elapsed between the date of the auditor's opinion and the balance sheet date (Habib, Bhuiyan, & Rahman, 2019); audit fees are higher if a fiscal year ends in accordance with a calendar year than if a fiscal year ends at a different date (McMeeking, Peasnell, & Pope, 2006;Tee et al, 2017); the length of cooperation with an auditor is inversely proportional to the amount of audit fees due to the smaller effort of the auditor in the process of recognising the weakness of internal control (Okolie, 2014) or the closer relationship between the auditor and the audited entity (Barkess and Simnett, 1994;DeFond, Raghunandan, & Subramanyam, 2002;Car-cello & Nagy, 2004). In turn, in his study, Knapp (1991) pointed out that, in the United States, the likelihood that an auditor will indicate significant irregularities increases in the first years of cooperation and then decreases reaching its minimum after 20 years of cooperation; reports other than the so-called clean opinions have a positive impact on the amount of audit fees (Verbruggen, Christiaens, Reheul, & Van Caneghem, 2015).…”