Purpose The choice between different financing sources is governed by a number of finance theories, particularly, trade-off theory and pecking order theory. However, the special characteristics of Islamic finance, which forces the exclusion of conventional bonds, leave Islamic banks with limited number of alternatives. Tier 1 sukuk are distinguished type of sukuk that combines the features of conventional bonds and stocks. This paper aims to answer the following question: Does the issuance of Tier 1 sukuk positively affect Islamic banks' profitability or is their impact concentrated on enhancing Islamic banks' capital adequacy ratios? Design/methodology/approach The data set used in this study consists of all United Arab Emirates (UAE) Islamic banks that issued Tier 1 sukuk over the period 2010-2020. Pooled and fixed effects panel regressions of Tier 1 sukuk and other control variables on three proxies of Islamic banks' profitability were run. The selection of fixed-effect model is based on Hausman test, redundant fixed effects and likelihood ratio test. Findings This study reveals novel findings. Tier 1 sukuk increases both earnings per share (EPS) and capital adequacy ratios. That is, this study finds that there is a positive significant impact of Tier 1 sukuk on EPS, which indicates that issuing more Tier 1 sukuk will generate more return to shareholders in terms of higher EPS because of the lower cost of Tier 1 sukuk compared to equity. However, this study finds that there is an insignificant impact of Tier on sukuk on both return on assets and return on equity. Hence, it is concluded that Tier 1 sukuk does not increase the risk appetite of UAE Islamic banks. Research limitations/implications Tier 1 sukuk is a niche instrument that has been recently used by Islamic banks. Hence, there are a limited number of Islamic banks that have issued this type of sukuk and consequently limited number of observations. Therefore, with the increased use of this instrument, a larger set of data will be available for examination. In addition, future research could examine the relationship between issuing Tier 1 sukuk and profitability in other countries where such sukuk have loss absorption feature. The impact of other types of sukuk, such as liability sukuk, on Islamic banks' profitability could also be an interesting field of study. Practical implications This study recommends Islamic banks to issue more Tier 1 sukuk to enhance their profitability indicators while meeting Basel III accord. This study also recommends investors to purchase the stocks of Islamic banks that issue Tier 1 sukuk because they are able to offer them higher EPS. The authors advise the UAE regulators to allow Islamic banks to issue Tier 1 sukuk with loss absorption feature to enable Islamic banks engage in more risky activities that usually provide larger profits. This study also suggests that the Islamic Financial Services Board (IFSB) reclassifies Tier 1 sukuk, with loss absorption feature, within the highest quality of capital, common equity Tier 1, to encourage Islamic banks to issue this type of sukuk, especially Basel III accord and IFSB 15 require higher ratios of common equity Tier 1 to risk-weighted assets. Originality/value This research contributes to the existing literature in two ways. First, it adds to the existing literature on the impact of sukuk on Islamic banks profitability. That is, contrary to prior studies that merely investigate the impact of issuing ordinary sukuk on profitability, this study explores a distinguished type of sukuk, that is Tier 1 sukuk, that has been surprisingly ignored so far. Second, this study shows that it is not only capital adequacy ratios that have improved as a result of issuing Tier 1 sukuk but also Tier 1 sukuk reduce the cost of capital of UAE Islamic banks which has been reflected in a higher profitability proxied by EPS. Hence, these sukuk serve a dual function for Islamic banks by improving both capital adequacy and profitability ratios.
