This thesis is an empirical investigation, examining how marginal tax rates on dividend income and marginal tax rates on wage income affect income mobility by letting two self-constructed income mobility indices be explained by tax variables in a multivariate OLS estimation of a distributed lag model. The mobility indices are obtained from Norwegian microdata containing population-wide income statistics. Aggregate mobility indices enter into a regression, where marginal tax rates on dividend and wage income are the main explanatory variables. In the identification of effects, the analysis takes advantage of tax reforms over the period 2000 – 2018, generating variations in tax rates over time. The motivation of the thesis is to provide information to policymakers on the relationship between taxation and income mobility, arguing that this is important for policymakers setting optimal tax rates. I find that an increase in the marginal tax rate on dividends increases income mobility with 1 percent in the short run and 0.6 in the long run when utilizing Shorrocks’ (1978) mobility index. Further on, a unit increase in the marginal tax rate wage income leads to a decrease in Shorrocks’ (1978) income mobility index by 1.6 percent in the short run and a decrease of 1.5 percent in the long run. The results for the index of Fields-Ok (1999) are however insignificant, signifying results being dependent on the index chosen.