This study examines whether tax sensitization campaigns can enhance tax morale and compliance intentions among Tunisian solo entrepreneurs, who often operate outside the formal tax system. Drawing on institutional theory, self-determination theory, and media richness theory, we test how communication formats shape compliance-related attitudes and intentions. A controlled 4 × 2 experiment with 500 entrepreneurs compares video, photographic, and SMS campaigns with a control condition. Results show a clear media richness effect, with video producing the strongest gains in tax morale and compliance intentions, followed by photographs and SMS. Perceived government legitimacy and tax morale mediate the relationship between campaign exposure and compliance intentions. Findings highlight the role of intrinsic motivation and institutional trust, among female and informal entrepreneurs. Perceptions of a dual zakat–tax obligation reduce the effectiveness of video-based messages. The study introduces and validates the ”Paying Twice?” scale capturing perceived fiscal burden from overlapping religious and statutory obligations.