If a decision maker's beliefs, values, prior experience, goals, fears, responsibilities and technical skill all influence the decision process then religion influences the decision process. How much, in what circumstances and what dissonance exists between decisions, personal beliefs and institutionalised coded beliefs (camel/eye of needle/rich man springs to mind) would be interesting questions. I'm about to look more into business ethics (really as underpinning CSR) so any good sources welcomed!
Religious conviction is highly influence decisions at the same time I am really havinag trouble finding what model we can develop to identify Christian business ethics. Does Christianity / Roman Catholicism have profound business ethics in practice.
When I learned about theory the definition of theory is any set of statements which explain facts or real observations that can be tested systematically in nature and affirmed or rebutted.
If what you mean by theory is similar to my generic definition of theory, then I argue that there is "business ethics theory." In the USA two companies come to my mind: Hobby Lobby and Chick-Fil-A.
These company founders are deeply religious and forgo hundreds of millions of dollars each year in annual revenues because they refuse to do business on Sunday. For Christians, Sunday is a day of rest and has deeply rooted significance in their faith. These facts (corporate behaviors) can be explained by a set statements which can be empirically tested by asking the right types of questions and answering them.
What theories of moral problems (consequentialism, utilitarianism) already exists that would explain an owner's valuing a day of rest and worship (Sunday) over bottom line profits? Business ethics theory evolves like any other theory. It evolves through the scientific process: gather evidence, write a specific hypotheses about the evidence gathered, and test the hypotheses to accept or reject them. Further the theory by publishing what you find for the scrutiny of others.
I am glad that you asked this question because it led me to conduct a search that revealed a business ethic theory that I had not heard of before; it is called Contractarian Business Ethics (article attached below). According to the Abstract, “Its stated ambition is to provide better practical guidance than the more general ethical theories of business ethics, such as Kantianism, pragmatism, utilitarianism, virtue ethics or the stakeholder model.” (Wempe, 2008).
Ref.:
Wempe, B. (2008). Contractarian business ethics: Credentials and design criteria. Organization Studies, 29(10), 1337-1355.