Dan Mayo is a Partner with over 25 years of professional tax experience in federal, international, and financial products taxation.
As the Lead for Withum’s National Tax Services practice, he helps businesses structure their affairs and plan transactions to minimize federal income taxes. He is experienced in mergers and acquisitions, capital markets transactions, and cross-border transactions, and he represents individuals and businesses in tax controversies with the IRS. Dan also serves as an expert witness in litigation involving tax issues.
Dan is a recognized expert in the areas of Qualified Small Business Stock (QSBS) and the Employee Retention Credit (ERC), and he co-leads Withum’s ERC Group. He keeps a pulse on federal income tax matters and upcoming legislation, and not only is he a thought leader within the Firm, but he is also an adjunct tax professor at Georgetown University Law Center, writing on all things tax and sharing best practices for minimizing taxes for businesses and HNW individuals.
Learn more about my professional experience and how I spend my time outside the firm.
As a tax professor at Georgetown University Law Center and an approved arbitrator for FINRA, Dan has an affinity for sharing his knowledge with others. He is a frequent speaker on webinars and at external tax conferences, and he writes for tax publications like the Daily Tax Report and Tax Notes Today. Previously, Dan served as the Chair of the Banking & Savings Institutions Tax Committee of the American Bar Association’s Tax Section.
Outside of the office, Dan’s hobbies include pickleball, tennis, swimming, and most importantly, spending time with family.
For years, S corporations have been the entity of choice for many closely held businesses. The structure offers pass-through taxation, generally avoids a second layer of tax and provides operational flexibility. But as founders of S corporations begin planning for a future sale, many discover one of the most powerful tax incentives available to business…
For decades, some tax advisors viewed First-Time Abate (FTA) relief as a one-time administrative benefit — valuable enough that some taxpayers intentionally chose not to use it for relatively small penalties in order to preserve it for a more significant issue later. That strategy may soon disappear. In a significant administrative shift, the IRS announced…
The question of who qualifies as a “limited partner” for purposes of Section 1402(a)(13) is now before the federal appellate courts, with potentially significant implications for partnerships and their owners. What began as a dispute over a narrow statutory exception for limited partners has evolved into a fundamental debate over whether self-employment tax liability should…
If you’ve received restricted stock, you have 30 days from the grant date to file an 83(b) election with the IRS. Missing this deadline can cause major tax issues down the road, and the IRS generally will not accept late filings. Still, there are some ways to help lessen the financial impact. Failure to timely file an 83(b) election means you will be taxed at ordinary income…
Treasury Department officials are discussing their concerns with Qualified Small Business Stock (QSBS) “stacking” strategies. Concerns were raised about stacking at two recent conferences; one official brought it up at the May meeting of the American Bar Association’s Tax Section, and another at a law firm-sponsored conference. Under the QSBS rules, each “taxpayer” is entitled…
The appeal many expected has arrived, but the real question is what comes next. For months, taxpayers and practitioners have wondered whether the IRS would ultimately accept the implications of Kwong v. United States or continue defending its interpretation of the COVID-era relief provisions under IRC §7508A(d). We now have part of that answer. The…
On January 16, 2026, the U.S. Court of Appeals for the Fifth Circuit issued a split decision (2–1) in Sirius Solutions v. Commissioner, a case with significant implications for partnership taxation. The ruling addresses the scope of the self-employment tax exclusion under Internal Revenue Code §1402(a)(13) and could reshape tax planning for limited partners in…
Are you a founder, investor or executive wondering if your business qualifies for powerful tax savings under the Qualified Small Business Stock (QSBS) rules? With recent updates from the 2025 One Big Beautiful Bill Act, commonly referred to as the OBBBA or OB3, understanding your eligibility and maximizing your benefits is more important than ever….