The aim of the TransFair-AT project was to analyse policy scenarios to achieve a complete decarbonisation of housing and mobility in Austria by 2040. This was achieved by linking a top-down macroeconomic model with bottom-up modelling of household vehicle choice, transport demand and building stock. The purpose of this model linkage was to assess the emission impacts as well as the macroeconomic and distributional effects of the policy packages on different types of households. The final objective of the project was to develop compensation measures to ensure that the disposable income of disadvantaged household groups was not reduced. The aim of this working paper is to give a summary of the methodological issues related to linking the top-down macro-economic model DYNK the bottom-up mobility model MARS/SERAPIS and the bottom-up building stock model Invert/EE-Lab. The paper is organised as follows. Section 1 gives a brief introduction, followed by section 2 summarising the results of a literature review about the state of art in linking top-down and bottom-up models. Section 3 gives a brief overview about the individual sector models utilised in TransFair-AT, while section 4 describes the process and results of model linkage in TransFair-AT. Finally, section 5 summarises the findings and draws conclusions.