How Germany's HSP GRUPPE builds an AI practice on ChatGPT Enterprise

OpenAI detailed how HSP GRUPPE, a German tax advisory network of roughly 100 cooperating offices nationwide, is building its ChatGPT Enterprise practice to boost productivity, improve work quality, and free up advisors' time for client work instead of routine tasks. The firm's enterprise contract with OpenAI has been in effect since January 1, 2024.

The rollout is driven by Carsten Schulz, HSP GRUPPE's co-founder, who also sits on the board of the Lower Saxony Chamber of Tax Advisors, where he chairs its AI committee. According to the network, ChatGPT Enterprise is used to draft job postings, cover letters, technical and marketing copy, and to help with standardized filings like objections to tax assessments — with servers hosted in Ireland and sensitive data not retained, keeping the setup compliant with data-protection requirements. Beyond ChatGPT, the network is also building out other AI tools: a platform called livestep for marketing, recruiting and internal office organization, and an early-stage pilot of Tabula, an assistant aimed at fully automated bookkeeping.

“Cooperation instead of a lone-wolf mentality.”

— Carsten Schulz, Co-founder, HSP GRUPPE

• HSP GRUPPE's enterprise contract with OpenAI has run since January 1, 2024
• The network spans roughly 100 tax advisory offices across Germany
• Beyond ChatGPT Enterprise, the network is piloting AI bookkeeping tool Tabula and platform livestep

The case study lands just as OpenAI keeps iterating on ChatGPT itself: this same week, the company updated GPT-5.6 Sol and expanded free access to GPT-5.6 Luna — meaning that alongside individual enterprise customer success stories, the underlying product keeps shifting toward greater accuracy and broader access.

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