Tax Court Calls Out AI-Fabricated Citations. Pro Se Filers Are Next.

You are representing yourself in Tax Court. You asked an AI tool to find cases that support your argument, and it gave you three case names with reporter citations that look exactly right. Stop—before you put any of them in a filing, you need to know what just happened to a lawyer in a Tax Court opinion called Clinco, and what happened to a self-represented litigant in a Michigan federal case called Lothamer.

One of them got a public scolding from the court. The other got a $2,900 bill.

If you have already used AI on a filing, take a breath—this is fixable, and you are not the only one (even the IRS has done it). Using AI to help you is not itself against the rules, and no one has been sanctioned simply for using it. People are sanctioned for filing citations they never checked. The fix is verification—not giving up a tool you may badly need.

What an AI "Hallucination" Is, and Why It Sinks Filings

When a large language model AI does not know the answer, it does not say so. It produces something that looks like an answer. In legal research that means invented case names, real-sounding reporter citations—a volume number, a page number—and confident summaries of holdings that do not exist anywhere. Lawyers call these "hallucinations." A more honest word is fabrications.

This is not a new or obscure problem. In his 2023 Year-End Report on the Federal Judiciary, Chief Justice John Roberts wrote that AI's "hallucination" shortcoming "caused the lawyers using the application to submit briefs with citations to non-existent cases. (Always a bad idea.)" That parenthetical—"(Always a bad idea.)"—has since been quoted by judges across the country, including the Tax Court.

Courts across the country have now documented hundreds of filings containing AI-fabricated citations—from both attorneys and self-represented litigants—according to legal researchers tracking the trend (see Damien Charlotin's widely cited AI Hallucination Cases database). The Tax Court has joined them.

What Happened in Clinco v. Commissioner

On February 9, 2026, the Tax Court issued a memorandum opinion—a full written opinion that is published and citable, though it carries less precedential weight than the court's "division" (T.C.) opinions—in Clinco v. Commissioner, T.C. Memo. 2026-16 (Docket No. 8077-23), written by Judge Holmes.

First, the part that is most important to understand: the fabricated citations in Clinco were filed by a licensed attorney, not a self-represented taxpayer. The petitioners were represented by counsel, Abraham R. Wagner, and the opinion repeatedly refers to him as "Clinco's attorney." This was not a pro se filing. Keep that straight, because the rest of this article is about why the case still matters enormously to people who represent themselves.

The underlying dispute was an ordinary one—a 2015 return, unreported restaurant receipts, disallowed rental depreciation, and penalties. The taxpayers argued that the IRS's notice of deficiency was invalid because a form was not signed in ink. The court rejected that argument on the merits and then turned to the cases cited to support it. Under a heading the court titled "Fabricated Case Citations," Judge Holmes wrote:

"The persuasiveness of Clinco's argument collapses like an overmixed soufflé when one looks at the citations used to prop it up. Mr. Wagner, Clinco's attorney, cites four cases in support. Three appear to be hallucinations generated by a large language model AI."

The court then walked through all three. Each followed the same pattern—a real-looking citation that, when you actually open the reporter to that volume and page, lands on a completely different case:

• Cacchillo v. Commissioner, 130 T.C. 132 (2008): does not exist. Page 132 of volume 130 of the Tax Court Reports falls inside Porter v. Commissioner, 130 T.C. 115 (2008), which discusses an unrelated standard of review.
• Miller v. Commissioner, 57 T.C. 440 (1971), as cited: does not exist as cited. Page 440 of volume 57 falls inside Winfield Manufacturing Co. v. Renegotiation Board, 57 T.C. 439 (1971), which says nothing about a notice of deficiency.
• Tefel v. Commissioner, 118 T.C. 324 (2002): there is no case by that name; page 324 of volume 118 is part of Hillman v. Commissioner, 118 T.C. 323 (2002), about management fees in an S corporation.

The court found it aggravating that the IRS had flagged the questionable citations in its brief, yet counsel did not explain them and listed one of the fake cases again in his table of authorities. Judge Holmes wrote that "the bouillabaisse of case names, reporter citations, and legal propositions suggests something cooked up by AI," that "their presence is unacceptable," and that "submitting a brief with fictitious caselaw is a recipe for sanctions and a clear violation of Rule 11(b) of the Federal Rules of Civil Procedure." The opinion reiterated Chief Justice Roberts's quip that doing this is "(Always a bad idea.)"

Now the second thing you need to understand: the Tax Court imposed no sanction in Clinco. A sanction is a penalty a court imposes for improper conduct—often a fine, sometimes worse. The opinion pointedly noted that other courts have begun to seriously sanction lawyers for this, then added, of the Tax Court: "has not done so. Yet." That word—"yet"—is why this is a warning shot, not a punishment. The court told everyone, on the record, that it sees this conduct, considers it unacceptable, and is signaling what comes next.

Why You Are Squarely Exposed Going Forward

It would be a mistake to read Clinco and think, "That was a lawyer's problem, not mine." The opposite is true. The pro se exposure is real, and it comes from three places.

First, the rule behind it reaches you. When you sign a Tax Court pleading, Rule 33(b) of the Tax Court Rules applies. Rule 33(b) says that "Counsel or a party signing a pleading certifies that the signer has read the pleading; that, to the best of the signer's knowledge, information, and belief formed after reasonable inquiry, it is well grounded in fact and is warranted by existing law." The rule reaches "Counsel or a party"—so it covers a self-represented petitioner's pleadings, not just a lawyer's. Signing your petition is itself a certification that you made a reasonable inquiry into the law you are relying on. The same idea appears in Federal Rule of Civil Procedure 11(b), which binds "an attorney or unrepresented party" alike. Clinco itself quoted Rule 11(b) in a footnote and identified Rule 33(b) as the Tax Court's only equivalent.

There is a nuance worth understanding. Rule 33(b) governs pleadings specifically—your petition, the IRS's answer, your reply. Briefs and motions are not "pleadings." For lawyers, the gap is filled by professional-conduct rules; a non-lawyer cannot violate lawyer-ethics rules because they are not a lawyer. That distinction is exactly what Judge Holmes addressed in a separate interview.

Second, the court is openly working out how to handle pro se AI misuse. In an interview with Bloomberg Tax, Judge Holmes discussed how the Tax Court would treat the same conduct from a self-represented filer. As reported by Bloomberg Tax, he said the court "wants to proceed gingerly," and that "if a pro se person does it, it's not really a violation of professional ethics because they're not lawyers, and we would have to figure out some other way of determining what the appropriate sanction is." Holmes reportedly said he has personally seen "fewer than a dozen" instances of hallucinated cases in the Tax Court and has not issued sanctions himself, and he floated that the rules committee might amend the rules to require a certification that AI was not used. The honest takeaway is not "you probably won't get fined." It is that the court will see through it, you will lose credibility, you may lose the argument, and the court is actively deciding how to respond. (Treat all of these as reported by Bloomberg Tax, not as a holding or a rule.)

Third, self-represented litigants do get fined for this elsewhere. In Lothamer Tax Resolution, Inc. v. Kimmel, No. 1:25-cv-579 (W.D. Mich.), Chief Judge Hala Y. Jarbou sanctioned a pro se litigant for AI-fabricated citations. The timeline is instructive: the court warned him on August 29, 2025, that future fictitious citations could result in sanctions; issued an order to show cause on November 19, 2025; and on December 1, 2025, imposed a monetary sanction. The court set it at $100 per false citation. It had identified 27 listed instances, but because two of them each contained two false citations, the total was 29 violations—29 × $100 = $2,900, payable to the Clerk of Court within seven days, with a warning that the per-violation amount would double for any future occurrence.

Two lines from that order matter for any self-represented reader. The court acknowledged the litigant "is proceeding pro se, and lacks the experience or resources available to an attorney," then held that pro se litigants "are not exempt from Rule 11 sanctions simply because they are not represented by counsel" and that the failure to make a reasonable inquiry "is sanctionable regardless of whether he is represented by counsel." And the court said it "need not make any finding as to whether" the litigant "actually used generative AI"—filing the fake citation is the violation, and blaming the AI is not a defense. Lothamer is a federal district court case, not the Tax Court, and it was a civil suit rather than a tax case. But it is the clearest illustration of what "some other way of determining the appropriate sanction" can look like for a non-lawyer.

What To Do If You Already Filed Something With an AI Citation

Many readers of this article are not asking "what if"—they have already filed a petition, motion, or brief with case citations an AI gave them. If that is you: do not panic, and do not stay silent. Silence is what the court found aggravating in Clinco—counsel was put on notice and said nothing. The protective move is the opposite: find out, and fix it first.

1. Verify what you already cited. Run every case in your filed documents through the routine in the next section. A citation that turns out to be real may still never have been read—check that the case actually holds what you said it does, not just that it exists.

2. If a citation is wrong or fabricated, correct the record promptly—before the IRS or the judge flags it. You can generally do this with a short, plain notice or letter to the court that identifies the bad citation, withdraws it, and either substitutes a correct authority or simply makes the argument without it. You do not need a case for every point; your statute and your facts can carry the argument. Owning the error early is treated very differently from being caught: Lothamer shows a court escalating warning, to show-cause, to a fine, and Judge Holmes indicated (as reported by Bloomberg Tax) that the Tax Court tends to let a self-represented filer re-argue without the fabricated case rather than sanction.

3. If you are not sure how to do this, get help now—not after your next deadline. A Low-Income Taxpayer Clinic can help you correct the record properly, free if you qualify, and this is exactly the kind of situation where professional help is worth it.

It Cuts Both Ways: The IRS Has Done This Too

This is not only a pro se problem, and you should not feel singled out. As reported by Bloomberg Tax, in Khoja v. Commissioner, Judge Jennifer Siegel ordered a hearing—held around March 11, 2026—to address an IRS motion that cited a non-existent case, and questioned the government attorney who signed it about apparent AI use and the office's safeguards. (We are relying on Bloomberg Tax's reporting here; no public written order has been located, and we state no docket number.)

The point is not that the government is careless. It is that AI fabrications can appear in any filing, from any party, including ones drafted by professionals with research budgets. That makes verification a universal discipline, not a pro se failing—and it is one you can do for free in a few minutes.

How To Verify a Case Is Real Before You File

First, learn to read a citation, because the whole trick depends on it. Take Porter v. Commissioner, 130 T.C. 115 (2008). It has parts: the case name; the volume number (130); the reporter—the book series—abbreviated ("T.C." is Tax Court Reports; "T.C. Memo." is the court's memorandum opinions); the page the case starts on (115); and the year. The AI tell Clinco exposed is a citation where the volume and page are real but point to a completely different case than the name claims. Once you can see the parts, you can check them.

Here is a free routine. Run it on every case cited in anything you file—especially a pretrial memorandum or a motion. Check the whole document, not just cases you added on purpose: AI tools often slip citations into a draft you never asked for, and a small-case (S case) filing is not exempt.

1. Check the Tax Court's own system (DAWSON). DAWSON is the Tax Court's official system for opinions, orders, and dockets. If a case is cited as a "T.C." or "T.C. Memo." opinion, or as any Tax Court case, and you cannot find it there, treat it as fabricated until proven otherwise.
2. Search Google Scholar case law (free), and actually open the result. Go to scholar.google.com and click Case law, then type the case name. Worked example: your AI gives you "Cacchillo v. Commissioner, 130 T.C. 132." Search the name. If no case with that exact name appears, it is almost certainly invented—this one was. If a result does appear, open it and confirm two things: the citation shown matches (volume 130, page 132) and the opinion actually says what your AI claimed. In Clinco, volume 130, page 132 was really part of Porter v. Commissioner—a different case on an unrelated issue. That mismatch is the fabrication.
3. Use CourtListener. CourtListener, from the nonprofit Free Law Project, is a free database of opinions and court documents, useful for federal trial and appellate cases.
4. Confirm statutes at Cornell LII. The Legal Information Institute hosts the authoritative free text of the Internal Revenue Code, the federal rules, and Supreme Court opinions. Use it to confirm a statute actually says what a source claims.
5. Confirm IRS material at IRS.gov. Check forms, notices, and guidance referenced in a filing directly against IRS.gov.

The habit, on every citation: (a) find the case by name in DAWSON or Google Scholar; (b) confirm the volume and page land on that case, not a different one; (c) read it and confirm it actually holds what you are citing it for; (d) if you cannot find it, do not cite it—and you do not need to swap in another case, because a self-represented argument can stand on the statute and your facts alone. Authority is not the same as evidence, but the discipline is the same one in How To Prepare Your Evidence For Tax Court: you must be able to put your finger on the source.

If the legal questions in your case are complex enough that you are leaning on AI to find supporting law, that is a strong signal to get help. A Low-Income Taxpayer Clinic may be able to assist for free if you qualify, and there is a point where professional help is the right call rather than a research shortcut that can backfire.

An Honest Note On How This Article Was Researched

TaxCourtHelp is an AI-assisted resource. We say that plainly because it is the whole point. AI is a genuinely powerful research aid for people who cannot afford a lawyer—the Chief Justice of the United States said as much in that same 2023 report, noting that for those who cannot afford a lawyer, AI can help with finding templates and court forms and answering basic questions, "all without leaving home," while adding that "any use of AI requires caution and humility."

That is exactly our posture, and it is exactly what we are asking of you. Every case, quote, rule, and number in this article was checked against the court's own opinion or order, the Supreme Court's website, or the Tax Court's rules. We did that because an unverified citation can sink your argument and your credibility—and because the same verification you just read about is one you can, and must, do yourself.

Resources

• Clinco v. Commissioner, T.C. Memo. 2026-16 (full opinion, CourtListener)
• US Tax Court Rule 33, Signing of Pleadings
• US Tax Court Rules of Practice and Procedure
• DAWSON — US Tax Court opinions, orders, dockets, and e-filing
• Federal Rule of Civil Procedure 11 (Cornell LII)
• 2023 Year-End Report on the Federal Judiciary (Chief Justice Roberts)
• Lothamer Tax Resolution, Inc. v. Kimmel — Dec. 1, 2025 sanctions order
• Google Scholar — Case law
• CourtListener (Free Law Project)
• Cornell Legal Information Institute

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax professional or attorney.