The aim of this research is to examine the impact of the board characteristics on sustainability performance disclosure and its reflection on the firm value. To achieve this objective, an applied study was conducted on a sample of (48) non-financial companies registered in the Egyptian stock market and listed in the S&P/EGX ESG Index during the period from 2015 to 2021, with a total of observations (336) observation, to test the three hypotheses of the research. The characteristics of the board size, board gender diversity, board independence, the combination of the positions of board chairman and CEO, and board activity; Sustainability scores provided by the Egyptian Stock Exchange were also used to sustainability performance disclosure, and Tobin's Q to express the firm value. Examining the impact of the board characteristics on sustainability performance disclosure and the impact of sustainability performance disclosure on the firm value was examined by relying on panel data models to analyze cross-sectional time data through the Stata program (Ver. 15). As well as examining the extent to which the board characteristics impact the firm value in the light of sustainability performance disclosure as an intermediate variable by using the path analysis model to study the direct, indirect and total effects between the variables of the assumed model through the AMOS program (Ver. 22).The results indicate that there is a significant positive impact of the characteristics of the board gender diversity and the board independence on the disclosure of sustainability performance, while the characteristics of board size, the combination of the positions of the board chairman and CEO and board activity did not have a significant impact, and there was a significant positive effect for the disclosure of sustainability performance on the firm value, and there was a significant positive impact of the board independence on the firm value in light of sustainability performance disclosure as an intermediate variable in the conducted companies.Based on this, the study recommends companies operating in the Egyptian business environment to increase the representation of women and independent members of the board structures, raise awareness of the importance of sustainability performance disclosure, and to oblige companies listed on the Egyptian Stock Exchange to environmental, social and governance performance disclosure along with financial reports or separately to achieve the sustainable performance, and The regulators adopting issuance an international accounting standard for the sustainability performance disclosure.

This study aims to measure the impact of corporate tax avoidance on the cost of equity (COE) in light of the agency theory in the Egyptian business environment as a model for the emerging countries' economies. To achieve this, aim the researcher examined the annual reports of a sample of corporations registered in the Egyptian stock market equals (64) non-financial firms listed on EGX100 index during the period from 2015 to 2019, with a total of observations of (320) observation to test the two study hypotheses. The researcher measured the corporate tax avoidance using three measures: Accounting Effective Tax Rate (AccountingETR), Current Effective Tax Rate (CurrentETR), Book-Tax Differences (BTD), in the main analysis, in addition to, the Long-Run Cash Effective Tax Rate (LRCashETR) in robustness checks, in order to give strength to the results of the study. The data were analyzed depending on the linear regression model according to the Ordinary Least Squares (OLS) method, and the Moderated Multiple Regression (MMR) model through program SPSS. The results indicate that there is a significant negative impact of corporate tax avoidance on the cost of equity, so the first hypothesis (H1) was accepted. The researcher also found that agency costs modify the relationship between corporate tax avoidance and the cost of equity. This result is consistent with agency theory, and the second hypothesis (H2) has been accepted. Based on that, the study recommends that firms operating in the Egyptian business environment should adhere to the income tax law, accounting standards and professional guidelines, and not engaging in tax avoidance practices, especially the aggressive one, aiming to reduce their tax. This is based on their social responsibility and the negative impacts of those practices on the state's public treasury.