The International Public Sector Accounting Standards (IPSAS) have driven the modernisation of public systems of financial information. The extent and pace of their implementation remain uneven. The goal of this study was to measure whether and how much governmental accounting standards converge towards IPSASs’ true and fair approach. The empirical context of the 26 Swiss cantons was used to apply a simplified maturity model. Under two successive reforms (maturity stages), each canton’s accounting standards were assessed and scored. The derived maturity levels indicate how close—or far—each canton has stood from a state of full IPSAS compliance (full maturity), at each stage of the process. As Swiss cantons have a certain degree of autonomy in setting their own accounting standards, the evolving paths they followed when implementing IPSASs were heterogeneous. The maturity level attained by each canton within each stage thus varies. However, the results show that the two successive reforms had an overall favourable impact on Swiss cantonal accounting standards compliance with IPSAS, and fairly improved the faithfulness of reported financial information. This research contributes to the international literature on public accounting standards and provides new insights for the assessment of convergence with IPSAS.