HSP GRUPPE, a network of legally independent tax advisory, auditing, and law firms, has spent over two decades digitising and standardising firm processes. When ChatGPT emerged, the network saw an opportunity to rethink how professional work itself could evolve rather than simply adding another productivity tool. Leadership asked what happens when AI becomes part of the operating model of a professional services firm.

That vision led HSP to embed ChatGPT Enterprise into tax advisory, legal research, client communication, financial analysis, and knowledge sharing. The rollout treated AI as an organisational transformation rather than a software deployment. Monthly AI forums gave employees a place to share practical use cases and learn from one another. ChatGPT Enterprise’s security features provided a technical foundation, while use of client-related information was governed by HSP’s internal data protection, confidentiality, and governance requirements. Professional review and final responsibility always remained with the relevant tax, legal, or accounting professional.

Across the firm network, professionals quickly found new ways to apply AI. HSP began standardising successful use cases into custom Agents. One example is AI Client Communication, a shared Agent that supports first drafts, structure, clarity, and a more consistent, client-oriented tone. Another is the Booking Assistant SKR03 & SKR04, which supports preparation and classification of specific booking questions. In both cases, the final professional decision remains with the employee. Managing Partner Frank Heibel described ChatGPT as a genuine sparring partner for working through complex tax questions. Partner Magdalene Posnak reduced the time to evaluate multiple real estate investments from nine hours to around two. Managing Director Marco Sell used AI-powered dashboards to explore financial scenarios with clients during meetings.

Results from the evaluation period (February 1 to July 14, 2026) showed 84% weekly active usage, 755 weekly active users, and 913 unique users. Users exchanged over 500,000 messages with ChatGPT. In a survey, 98.6% of employees reported higher productivity, 84.6% reported improved quality of work, and 95.9% reported weekly time savings; 63.5% saved at least two hours per week, and 25.7% saved at least five hours. 79.7% reported better client service and 78.1% higher job satisfaction. A deliberately conservative internal scenario estimated approximately 40,000 hours of additional annual capacity, with roughly 28,000 hours supporting productive, generally billable specialist work and 12,000 hours supporting administration and client service. Based on conservative hourly rates, HSP estimated a theoretical annual revenue potential of approximately €3.8 million. This is a capacity scenario, not realised or guaranteed revenue.

HSP is now preparing for the next phase with ChatGPT Work. The organisation began piloting the platform with a small group of developers and administrators before expanding. The goal is to understand how agentic AI can safely automate complex workflows while balancing governance, quality, and cost. HSP’s leadership lessons include treating AI as an organisational capability rather than an individual tool, scaling successful experiments into repeatable workflows, investing in operational foundations first, creating a culture of continuous learning, redesigning end-to-end workflows rather than automating isolated tasks, and building AI around professional judgment. Future plans include establishing a joint DATEV-centric AI, firm process, and development team with Kanzleipakt to translate successful experiments into documented reference workflows.