Should I use a tax attorney for an offer in compromise?

If you're being threatened with prosecution, then a tax attorney is the way to go. For an OIC,, an enrolled agent can do the job and will cost a lot less. Whichever way you go, quiz the person on how many OIC's they've done and how many have been successful.

Yes, you should retain an experienced tax relief attorney to resolve your tax debt. My answer is biased as I am a tax relief attorney. A $400K tax bill is a significant tax debt that requires a tax attorney's professional experience and advice. While it is possible to resolve a tax liability on your own, or by using other tax professionals, I personally believe you get a better result if you hire a tax attorney, as you would in any legal matter. An analogy I provide to my clients is that of a mechanic. If your car breaks down, you could fix it yourself; you just don't have the training or experience to do so. So, most people take their cars to a mechanic to repair because mechanics have the proper training and experience to get the best result possible in fixing the car. Resolving a tax debt is no different. In regards to your question of how to be sure that an attorney has actually had prior success with an offer in compromise, it would be unethical for an attorney to tell you that they have had prior success with filing offers in compromises if they have not had any success. However, they will likely not be able to get into specific prior client successes unless the prior client has authorized the attorney's use of their information. Additionally, past successes cannot be an assurance of future successes because each case must be decided on its own merits and will differ if based on different facts.

you can certainly do your own the entire deal with the OIC is offering a figure that IRS will accept and only you know what that figure is you can certainly complete the paper work yourself without paying high legal fees a tax attorney will not be any better than other tax professionals, they are all educated in the same rules and regulations