The Dutch market for mandatory audit services is heterogenous and includes publicly listed and private firms. While private firms dominate the market, existing audit research focusses primarily on listed firms where audit demand originates from external stakeholders such as shareholders assisting them in the monitoring of management. This is surprising as private firms represent a significant portion of the economy in most countries. Private firms generally face different incentives in terms of accounting and auditing demand. For example, private firms that are not run by owner-manager may have agency conflicts that drives the demand for audit. However, in private owner-managed firms external audit demand can arise from other, more internal, factors that are difficult to observe and less well understood, such as compensation for lacking internal controls. Legislators across the world seem to acknowledge this variation and mandate audits to a varying degree, for instance dependent on private firm size. Yet, institutional heterogeneity is large, varying from mandating audits for very few (e.g., United States) to all (e.g., Sweden) private firms. Furthering our understanding of internal value factors of private firm external audits and their effect on audit pricing, audit effort and audit quality is therefore relevant. It can assist regulators in determining the scope (which private firms) and features of a private firm audit (e.g. independence regulation, exclusion of certain non-audit services). Understanding internal value factors can assist auditors and audit firms in how to price and ‘produce’ private firm audits and the effects of these decisions on audit quality.