Concept Tax-benefit microsimulation models are used to answer “what if” questions about the effects of tax and benefit reforms on household incomes and the income distribution. Such analysis is regularly performed for Budget and other Government policy announcements and is also highly relevant for the design of alternative reforms and new policy instruments. What is tax-benefit microsimulation? What is UKMOD? Why use UKMOD? Key strengths of the model include: The only accessible model for the UKComparability with the EUROMOD EU-27 modelHighly flexible policy settingsIntuitive user interfaceSpecial-purpose tax-benefit modelling languageExtensive library of policiesContinually updated and developed How does UKMOD work? UKMOD applies user-defined tax and benefit policy rules to harmonised microdata on individuals and households, calculates the effects of these rules on household income, and then outputs results – still at the micro level. The user interface can output a range of summary statistics, including (changes to) risk-of-poverty and income inequality and the (net) budgetary cost of policy changes.