what is the procedure for catching up on back taxes owed

This answer does not create an attorney-client relationship. FInd the money and get the returns prepared. Then file them. Then prepare to file an Offer in Compromise. You may want to go ahead and file for the Offer in Compromise, or you may want to wait, depending on your situation. If you wait, don't wait until the IRS starts taking your property!!! You will get IRS Notices in advance of any taking.

An attorney familiar with the Offer in Compromise program should be able to assist you. I would stay far away from the OIC companies that advertise nationally.

In addition to the answer provided by my colleague, it is important to realize that while the failure to file returns is a federal misdemeanor (as is a failure to pay), the continued failure to properly account for and pay taxes can viewed as a felony evasion violation if enough "intent" evidence can be developed by the IRS. The initial goal, of course, is to avoid any criminal charges -- which is why resolving the problem as soon as possible is important. As the old adage points out, there are few things certain in life--other than death and taxes. Information about the statutes, penalties, and procedures of the Tax Division of the U.S. Department of Justice are provided in the US Attorney's Manual. The IRS also explains its procedures in depth on its website in its Internal Revenue Manual.

DISCLAIMER
This answer does not, nor is it intended to, create an attorney-client relationship or constitute attorney advertising. Rather, it is offered solely for information purposes. Since the facts of each case are different, it is important to seek out qualified counsel with whom information can be shared and assessed under an attorney-client privilege so that competent and tailored advice can be provided.