Integrated microsimulation and CGE model as a tool for regulatory impact assessment This paper presents the integrated tax-benefit microsimulation and computable general equilibrium (CGE) model for the Polish economy. The tool has been designed to enable the ex ante regulatory impact assessment of fiscal and social policy. Proposed regulatory changes are evaluated along three dimensions – financial, distributional and macroeconomic. The microsimulation model incorporates estimated mechanisms enabling behavioural responses of private households in terms of consumption and labour supply. These responses serve as first-step linkages between the models (e.g. an increase in household expenditure determined in the microsimulation model translates into an increase in demand for individual commodities in the CGE model). The primary objective of the general equilibrium model within our modelling framework is to track the economy-wide effects of a given policy shock. These include the impact on output, employment, prices, balance of trade, household and general government income etc. In the second step macroeconomic effects of proposed regulations are passed from CGE to microsimulation model and alter the behaviour of households. The models are fully integrated, i.e. the iterations are repeated until there is no significant change in the outcomes. As an example of the model’s application the reform of the Polish personal income tax system is presented.