We present a model for assessing how the UK’s system of market-based finance — an increasingly important source of credit to the real economy since the financial crisis — might behave under stress. The core of this model is a set of representative agents, which correspond to key sectors of the UK’s financial system. These agents interact in asset, funding (repo), and derivatives markets and face a range of solvency and liquidity constraints on their behaviour. Our model generates ‘tipping points’ such that, if shocks are large, or if headroom relative to constraints is small, lower asset prices can cause solvency/liquidity constraints to bind, resulting in forced deleveraging and large endogenous illiquidity premia. We illustrate such an outcome via a stress scenario in which a deteriorating corporate sector outlook coincides with tighter leverage limits at key intermediaries. Our findings highlight the key role played by broker-dealers, commercial banks, investment funds and life insurers in shaping these dynamics.