Background: Standardised cost and resource data are crucial for Health Technology Assessment (HTA) and healthcare planning. While many countries have national health economic guidelines, Austria lacks a consensus on a health economic reference case and costing standards.

Methods: This project analysed health economic guidelines, costing manuals, and HTA documents from 59 countries using a multi-stage approach based on ISPOR guidelines and systematic reviews. Data on reference case characteristics and detailed costing processes were extracted and synthesised narratively and in tables.

Results: Costing universally involves identification, measurement, and valuation, with the chosen perspective (e.g., healthcare, societal) being the primary determinant of cost inclusion. The analysis of 12 countries with detailed guidelines reveals a high level of methodological maturity and consensus on core principles like uncertainty analysis. However, significant divergence exists in practice. While bottom-up micro-costing is the gold standard, most countries adopt a pragmatic top-down approach, except the Netherlands which mandates "micro-costing first". Perspective choice creates three clusters: strict healthcare (e.g. Australia), social health insurance (Germany), and comprehensive societal (e.g. the Netherlands). The Netherlands is unique in formally including cross-sectoral costs like education and justice. Valuation is predominantly tied to national tariffs or specific unit costs.

Discussion: The choice of perspective is the most consequential decision, shaping all subsequent steps. A country's data infrastructure fundamentally dictates feasible costing methods. For Austria, developing a national guideline requires explicit decisions on the adopted perspective, the balance between precision and pragmatism in costing approaches (recommending a mixed approach), and specific methodological stances on productivity costs, discounts, and cross-sectoral impacts.

Conclusion: International guidelines offer a framework of methodological flexibility for Austria. The central decisions involve the politically charged choice of perspective and the definition of relevant costs. This report provides a foundation for developing an Austrian reference case, with next steps including an analysis of national cost data sources to inform a formal guideline development process.