As per our company policy, we do not provide this service. We view it akin to someone asking a doctor, "Can you have a quick look at this thing I have and let me know if you think it's bad?" The standard answer any competent doctor would give is: "Sure, please come for an appointment first thing on Monday, and we'll run some tests."
For the same reason, we don't do back-of-the-envelope estimates for taxes owed, for example, before the April 15th deadline. Our approach is one of thoroughness and accuracy, entailing the complete preparation of your return, allowing us to provide you with precise information about your tax obligations, or even better, the size of your potential refund.
Our rationale behind this is rooted in the understanding that estimates can often prove to be inaccurate (which is why they are referred to as estimates). We refuse to take the chance that a piece of information we give to our clients could potentially be erroneous or misleading — information upon which they may base significant financial decisions.