Purpose -The purpose of this paper is to provide evidence concerning the effective use of qualitative materiality factors (QMF) included in the new ISA 450, and its potential consequences from the perspective of Spanish independent auditors and preparers of financial statements. Design/methodology/approach -A specially designed questionnaire was distributed to a sample of both (352) auditors and (121) preparers in Spain. Frequencies and ranking comparisons, Student's t-tests, and Mann-Whitney tests were used to analyse the data. Findings -Results show that the majority of auditors and preparers that participated in the study agree on the issuance of qualified audit reports when the financial statements contain uncorrected misstatements that are below the materiality levels but are related to QMF included in ISA 450. Furthermore, both groups accept that this situation would have important positive effects on the development and results of current practice in auditing, on the quality of financial statements, and on both users and society. Research limitations/implications -First, as with all mail surveys, there are some limitations associated with individuals' responses. Second, the findings of this paper should be interpreted bearing in mind that the survey was conducted before the new ISA 450 was published in October 2008. Finally, this paper is limited to the Spanish context; thus, the findings may not be applicable elsewhere. Practical implications -The findings of this paper have significant practical implications for auditors, as well as for policy makers, enabling them to better understand the importance of the qualitative side of materiality in auditing judgments. Originality/value -From the perspective of both auditors and preparers, this paper provides evidence about the QMF included in the new ISA 450, effective for audits of financial statements for periods beginning on or after December 15, 2009.