Bilancio: An instrument-level balance-sheet simulator for monetary economics

• Instrument-level simulator where agents are balance sheets. • Tracks dated cash flows with explicit means-of-payment constraints. • Payments succeed or fail based on liquidity, enabling default cascades. • Includes Treynor-style dealer pricing kernels for market intermediation. • Open-source Python with YAML scenarios and comprehensive documentation. Bilancio is an open-source Python framework for simulating monetary and financial systems at the instrument level. Unlike traditional approaches that represent money as aggregate stocks or equilibrium prices, Bilancio models agents as explicit balance sheets, tracks individual financial instruments with dated cash flows, enforces double-entry accounting, and treats payments and defaults as concrete events. The framework implements dealer and bank pricing kernels derived from market microstructure theory, enabling researchers to study phenomena where the timing of payments, the hierarchy of settlement media, and balance-sheet constraints jointly determine outcomes. Bilancio supports declarative YAML-based scenario configuration and programmatic Python APIs, with optional cloud execution and interactive visualization. All examples run locally without external dependencies.