Discourse within academic and professional literature emphasises the need for small and medium practices (SMPs) to re-evaluate their current services, requiring a review of their value proposition and an eventual change to their business model (IFAC, 2018a). This stems from a range of global challenges, including falling profit margins from compliance work, technological and regulatory developments, changing client needs, and competition for talent, pressuring their traditional service offering (Lander, Koene and Linssen, 2013; Street et al., 2019). To remain viable, the Edinburgh Group called for SMPs to extend their services beyond compliance work (Street et al., 2019). This involves adapting their business models (Hedman and Kalling, 2003) and leveraging their tangible and intangible knowledge-based resources therein, conceptualised as intellectual capital (Duff, 2018), to sustain competitive advantage (Petty and Guthrie, 2000; Fu et al., 2017). Few studies have examined how SMPs adapt in practice (Lander, Koene and Linssen, 2013). This literature gap, coupled with a research agenda for the SMP (Ramirez, Stringfellow and Maclean, 2015; Ali and Mustafa, 2023), provides the motivation for this study, which specifically investigates the Chartered Accountancy SMP in Ireland. Adopting an interpretivist methodology, this 11 case-site study, supported by 33 semi-structured interviews, practice profile questionnaires and triangulation evidence investigates the interplay within the BM, between prevailing institutional logics (Thornton, Jones and Kury, 2005) and the institutional work (Lawrence and Suddaby, 2006) undertaken in response to challenges, thereby extending Hedman and Kalling’s (2003) BM conceptualisation. It also develops a continuum-based scale for assessing SMP institutional logic, adapts Farooq and de Villiers’ (2019) model for institutional work to incorporate actor reflexivity and agency, develops a novel Institutional Orientation Typology capturing the relative mix of institutional work undertaken, and proposes an archetypal-scoring framework (Greenwood and Suddaby, 2006) situating this study’s case sites along an archetype continuum.