The study aims to investigate the impact of debt on corporate profitability in the context of Vietnam. The paper investigates the impact of debt on corporate profitability in non-finance listed companies on the Vietnam stock market. The panel data of the research sample includes 118 non-financial listed companies on the Vietnam stock market for a period of nine years, from 2009 to 2017. The Generalized Method of Moments (GMM) is employed to address econometric issues and to improve the accuracy of the regression coefficients. In this research, corporate profitability is measured as the return of EBIT on total assets. The debt ratio is a ratio that indicates the proportion of a company’s debt to its total assets. Firm sizes, tangible assets, growth rate, and taxes are control variables in the study. The empirical results show that debt has a statistically significant negative effect on corporate profitability. The result also shows this effect is stronger in a non-linear (concave) way, we show that the debt ratio has nonlinear effects on corporate profitability. From this, experimental evidence shows that the optimal debt ratio is 38.87%. This evidence provides a new insight to managers of the non-finance companies on how to improve the firm’s profitability with debt.

Abstract
1. Introduction
2. Data and Variables
    2.1. Data Description
    2.2. Variables
3. Methodology
4. Correlation Analysis
    4.1. Partial and Semi Partial Correlations
    4.2. Correlation between the Variables
5. Econometric Analysis
6. Conclusion
References

• Van Toan NGO(Faculty of Finance – Banking, University of Finance – Marketing (UFM), Ho Chi Minh City, Vietnam) Corresponding Author
• Thị Xuan Huong TRAM(School of Banking, University of Economics Ho Chi Minh (UEH), Ho Chi Minh City, Vietnam.)
• Ba Thanh VU(Food Farm Company Limited, Ho Chi Minh City, Vietnam)