Iranian Accounting Standard No. 35, which became mandatory in 2020, was introduced to distinguish financial reporting from tax reporting and to recognize income tax expense on an accrual basis. Nevertheless, professional evidence indicates the continued misalignment between the requirements of this standard and the Direct Taxation Act. Previous studies have predominantly examined this inconsistency through isolated case-based or single-variable analyses and have not provided a comprehensive, validated framework encompassing both implementation challenges and corresponding improvement strategies. Accordingly, this study adopted an exploratory sequential mixed-methods design. Qualitative data were collected through 17 semi-structured interviews with experts and analyzed using Braun and Clarke’s six-phase thematic analysis. The resulting themes were subsequently validated through a two-round Fuzzy Delphi technique. The thematic analysis yielded 204 initial codes, which were organized into seven overarching challenge themes, seven overarching solution themes, and one cross-cutting cluster. Inter-coder agreement reached 0.82, indicating substantial coding reliability. In the Fuzzy Delphi stage, all 14 indicators achieved defuzzified values ranging from 0.738 to 0.898, exceeding the acceptance threshold of 0.70; consequently, no indicator was eliminated. The questionnaire demonstrated satisfactory reliability across the two Delphi rounds, with coefficients of 0.72 and 0.88, respectively, while stopping criteria were confirmed using analysis of variance (ANOVA) and chi-square tests. The findings reveal that a fundamental paradigmatic conflict constitutes the common root of the identified implementation challenges. Therefore, improving the implementation of Accounting Standard No. 35 requires a comprehensive, multilayered, and simultaneous package of institutional, regulatory, educational, and operational interventions.