Research have revealed that the accounting profession engage multi-disciplinary teams in the assurance of sustainability reports. However, how such teams are composed or the values that these teams bring to the assurance engagement process, and how reliance is established on the work performed by such teams has been left uncovered. This research sought to fill this gap, and hence, contributed to providing an understanding surrounding this issue. Semi-structured interviews with auditors from the Big Four Audit firms, engaged with performing sustainability assurance was conducted. The findings revealed that the engagement of multi-disciplinary teams, comprising both financial accountants and sustainability specialists from various disciplines, was necessary in ensuring quality assurance work performance. Firstly, the in-depth knowledge of sustainability subject matters possessed by the sustainability experts, enabled the questioning of the correctness of sustainability items reported by the clients. Secondly, sustainability experts were valuable in the planning stage of the engagement, in identifying client risk areas. Thirdly, sustainability expert involvement, enabled the winning of work contracts. Additionally, the engagement of multi-disciplinary teams was revealed to be valuable to the client firms. Firstly, the sustainability experts assisted clients in identifying the most valuable issues to report to their stakeholders. Secondly, due to the expert’s knowledge and experience, it enabled them to inform clients on high reporting levels. Finally, sustainability experts provided clients with valuable feedback that aids the improvement of the client processes, and the management of risks. The establishment of reliance on the work performed by the teams, requiring an accountant to signoff every engagement work performed by the team, as required by the applicable assurance standards, was partially supported by this study. Sustainability experts, who were non-accountants, was revealed to be engaged in this signing off ritual, hence, leaving room for the questioning of such assurance engagements signed off by sustainability experts.

Non-audit services provided by audit firms have been a popular scientific topic within the fields of audit and accounting research over the past decades. Numerous researchers have attempted to provide a theoretical contribution by examining different ways of measuring the concepts of audit quality and financial reporting quality. The resulting consequences are mixed results and a lack of consensus among researchers from both research fields. The two, in other situations, rather distinctive research fields of audit quality and financial reporting quality, have, in several cases, been confounded without analytical reflection regarding their differences. In parallel to the scientific progress, regulatory bodies have noticed the increasing trend of non-audit services and how they constitute larger portions of the audit firm’s annual revenues. Their responses have been legal restrictions, both in the US and Europe, in order to cease the trend. The purpose of this thesis is to make a pronounced investigation regarding the relationship between non-audit services and financial reporting quality in Swedish private firms. Furthermore, it will also be of interest to examine if this proposed relationship is moderated by the presence of the four global market-leading audit firms or not. The study is based on a deductive approach and a quantitative research strategy, to collect and analyze data from annual reports. To fulfill the purpose of the study, the data is analyzed by conducting binary and multinomial logistic regression tests. The results suggest that there is an association between certain types of non-audit services and financial reporting quality. Specifically, services that are unrelated to tax have proven to be statistically significant positively correlated with financial reporting quality. No evidence was found supporting a moderating effect by the characteristics of audit firms, suggesting that the choice of an audit firm is irrelevant for attaining high financial reporting quality when purchasing non-audit services. The study’s theoretical contribution is the novelty arising from the combination of studying non-audit services’ impact on financial reporting quality within a Swedish setting on private firms. The study also provides empirical contribution by using a proxy for financial reporting quality rarely used in previous research. The findings are of practical importance since they suggest that firms potentially benefit in their financial reporting by purchasing these kinds of services, which contradicts past actions made by regulatory bodies.