This paper explores the impact of fiscal policy on long-term economic growth, focusing on models that allow for endogenous growth. The authors argue that if the social rate of return on investment exceeds the private rate, tax policies that encourage investment can boost growth and utility levels. Conversely, if the private rate of return equals the social return, no such incentives are necessary. The paper discusses various models, including those with learning-by-doing, public services, and technological progress. It highlights that in models with public services, the optimal tax policy depends on the characteristics of these services. For example, lump-sum taxation is more efficient for publicly provided private goods, while income taxation is better for congestible public goods. The authors also examine models with technological progress, where the growth rate is influenced by the expansion of capital varieties or consumer product varieties. They conclude that in models with adjustment costs, the interest rate and growth rate are negatively correlated, and in models with varieties of consumer goods, the required premium on future consumption is independent of the growth rate. Overall, the paper provides insights into how fiscal policies can influence economic growth and the optimal tax structures for different types of public services and technological advancements.This paper explores the impact of fiscal policy on long-term economic growth, focusing on models that allow for endogenous growth. The authors argue that if the social rate of return on investment exceeds the private rate, tax policies that encourage investment can boost growth and utility levels. Conversely, if the private rate of return equals the social return, no such incentives are necessary. The paper discusses various models, including those with learning-by-doing, public services, and technological progress. It highlights that in models with public services, the optimal tax policy depends on the characteristics of these services. For example, lump-sum taxation is more efficient for publicly provided private goods, while income taxation is better for congestible public goods. The authors also examine models with technological progress, where the growth rate is influenced by the expansion of capital varieties or consumer product varieties. They conclude that in models with adjustment costs, the interest rate and growth rate are negatively correlated, and in models with varieties of consumer goods, the required premium on future consumption is independent of the growth rate. Overall, the paper provides insights into how fiscal policies can influence economic growth and the optimal tax structures for different types of public services and technological advancements.