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Civil Tax Controversy

Audit Defense

Since 2005, McMahon & Tivnan has consistently achieved the best possible results in IRS and State tax audits because of our vast experience and knowledge of the audit process. Our attorneys are guided not only by our understanding of Internal Revenue Code, but also by our expertise in IRS examination rules and procedures.

Several of our professionals including our founder worked for either the IRS Office of Chief Counsel or the IRS Office of Appeals. Since 2014, D. Sean McMahon has taught the Tax Practice and Procedure course at The Boston University School of Law Graduate Tax Program, a graduate degree program for attorneys. All of our professionals focus exclusively on tax controversy matters and achieving the best results possible.


McMahon & Tivnan regularly represents individuals, estates, and businesses facing IRS and state collection matters. Our attorneys have expertise working with the IRS and state agencies throughout all stages of the collections process starting with the first notice of an amount due all the way through appeals. Our firm’s objective is to negotiate and resolve collections matters quickly, efficiently, and successfully.

Offers in Compromise & Installment Agreements

The IRS and state agencies may allow taxpayers to settle a liability for less than the full amount or enter into installment agreements to pay off their liability. McMahon & Tivnan has successfully negotiated hundreds of settlements and installment agreements, saving our clients up to millions of dollars. Our attorneys’ extensive familiarity with how the IRS and state agencies analyze these Offers make our firm uniquely qualified to negotiate the best settlement for our clients to maximize tax savings and minimize exposure of taxpayer’s assets.

Innocent Spouse

In general, spouses who file joint income tax returns are jointly and severally liable for any tax reported on those returns, which means the IRS can pursue either spouse for the entire amount of tax due. However, the IRS may provide relief for certain qualifying taxpayers.  \McMahon & Tivnan have helped scores of taxpayers successfully defend their innocent spouse claims, absolving them of their obligation to pay tax liabilities they are not responsible for. Innocent spouse matters can be highly personal for taxpayers and our attorneys take a tailored and unique approach to each client’s situation.

For a more in depth discussion on whether you may qualify for innocent spouse relief, please read our blog post.


McMahon & Tivnan achieves superior settlements at IRS Appeals by understanding the IRS Appeals procedures and demonstrating the IRS’s hazards of litigation if it proceeds to trial. The IRS determines settlement amounts by evaluating the risk presented by the taxpayer’s position at trial. McMahon & Tivnan have a long, successful trial record in tax cases against the IRS. IRS Appeals is aware that our attorneys are well-qualified and have successful experience trying tax cases. Clients represented by McMahon & Tivnan always present a serious litigation risk which helps achieve agreed resolutions.


McMahon & Tivnan’s documented trial wins against the IRS and state tax authorities separates us from other tax professionals. Unlike many tax professionals, McMahon & Tivnan attorneys not only have the expertise to understand the most complex tax situations, but have also achieved published trial success in the United States Tax Court and other Federal Courts.

Most tax disputes are resolved by agreement, however, if the government decides not to settle a case or make an unreasonable settlement offer you need trial counsel with tax trial experience. Whether the IRS has overstated the value of a closely held company by $68 million; falsely claimed a taxpayer willfully failed to report a foreign bank account and income; or claimed a lien interest in property not owned by the taxpayer, Federal Courts have consistently ruled in favor of McMahon & Tivnan’s clients, including ordering the IRS to pay its legal fees.