I am still growing this business so why would I turn away clients? The key word here is "want".
There are returns that I try to avoid. I have training in partnership and corporation returns but I screen clients with those returns and only take the returns I am comfortable in preparing correctly. It is not in the client's best interest for me to "try" the return. I don't have anyone who can properly check the return. Also,I don't set up retirement or cafeteria plans. There are good firms that have experience in these fields and this is one time you get what you pay for. This is doing what is best for the client.
No, complexity has nothing to do if I "want" to take or keep a client. It has to do with the client and what they perceive as my role in the process. My job is to prepare a correct return for them based on the information they provide and my interpretation of the tax code. As part of the job I will listen to rants about the tax system or how miserable their life is. I will explain the same tax issue until they understand it. I will answer their questions and what ifs. I consider all that part of the job.
The clients I don't want are the clients who try to change my job description to get what they want. It is not my job to fill in the blanks so that they pay what they want to in tax or get the refund they want. It is not my job to lie (BS) to the IRS when that trick they used to play the system backfires. It is not my job to get in the middle of a divorce or family argument. It is not my job to do what their previous preparer did if it is wrong. It is not my job to be bullied because they don't like the results.
If the services I offer are not what a client wants in a tax preparer, I understand if they look for another preparer. And I will help them make that decision if they can't do it themselves.