This article reports on a project introducing techniques from the MUST method for IT designers in a large international supplier of systems for tax assessment and auditing. The focus is on evaluating the fit between the supplier's system and the customer's requirements, particularly through meetings aimed at aligning top management with the supplier’s analysis. The article describes the MUST method’s anchoring principle and the technique of problem mapping supporting this principle. This participatory approach resulted in mutual learning processes with top management which is rarely reported on in the PD community. Top management participated by reviewing, challenging, and reformulating the IT designers’ central suppositions, assumptions, and hypotheses related to the causal relation between identified problems and suggested solutions.