We’ve all been there. A client walks into your office and, somewhere in the conversation, you realize that a seemingly minor oversight, a missed deadline, a form nobody filed, an election nobody mentioned, has spiraled into a five- or six-figure tax problem. In my years of practice, some of the most expensive mistakes I’ve seen weren’t the result of aggressive planning gone wrong. They were small, quiet errors. The kind that happens when a deadline slips, an election isn’t made, or a form gets overlooked entirely. The tax code is unforgiving in these situations, and the IRS has little sympathy for “I didn’t know.” This article walks through some of the most common, and most costly, small mistakes that can devastate your client’s tax situation, along with practical guidance for avoiding them.

Tax professionals are inundated with tax developments from all branches of the government and from all levels of government on a daily basis. Our technical tax knowledge expands weekly. Given the immensity of tax law changes in P.L. 119-21 (July 4, 2025), informally named the One Big Beautiful Bill Act (OBBBA), and the guidance we’ll continue to get over the next few years along with non-OBBBA updates, we might run out of time and bandwidth to step back and ask what additional relevance this guidance, as well as various reports issued by the government every day, mean for the well-being of our tax system. This article unpacks select tax law changes and government documents to offer four subtle messages within them. Generally, the messages don’t bode well for an effective tax and revenue system. The article ends with some suggestions on what can help improve our tax system.