Use caseFor tax and legal
Check the facts in your memo before you sign it.
Lenz is a fact-checking service for tax and legal memos. It identifies the factual statements it can check against independent public sources — what a statute requires, what a court held, a rate, a deadline, a form number — and returns a result for each. It is not a citator.
Private by default. Zero retention on paid Pro and Scale.
Example: a tax memo“A calendar-year C corporation files its federal income tax return on Form 1120, due April 15, and can extend the deadline by six months by filing Form 7004. An S corporation files the same Form 1120 by the same date.”
FalseAn S corporation generally files Form 1120-S for its federal return.
Mostly FalseCalendar-year S corporations generally file federal returns by March 15.
- A result per statementeach one comes back on its own
- Every check is datedand so is every source
- Comments and edits in your Word filecomments and tracked changes
01Example
Five statements. Two need correcting.
| Claim | Verdict | Lenz Score | Sources |
|---|---|---|---|
| A calendar-year C corporation files its federal income tax return on Form 1120. | Truehigh confidence | 9/10 | irs.govthomsonreuters.comfreshbooks.com+3 more |
| A calendar-year C corporation’s federal income tax return is due on April 15. | Truehigh confidence | 9/10 | ecfr.govfederalregister.govirs.gov+17 more |
| A calendar-year C corporation can obtain an automatic six-month extension to file its federal income tax return by timely filing Internal Revenue Service Form 7004. | Truehigh confidence | 9/10 | ecfr.govirs.govuscode.house.gov+10 more |
| An S corporation files its federal income tax return on Internal Revenue Service Form 1120.Suggested rewriteAn S corporation files its federal income tax return on Internal Revenue Service Form 1120-S. | Falsehigh confidence | 1/10 | irs.govuscode.house.govturbotax.intuit.com+2 more |
| An S corporation has an April 15 federal income tax return filing deadline.Suggested rewriteA calendar-year S corporation has a March 15 federal income tax return filing deadline. | Mostly Falsehigh confidence | 3/10 | uscode.house.govgovinfo.govecfr.gov+14 more |
Deep check · Checked 2 September 2026.
Open a row for the sources it used and the reasoning that weighed them.
02What is checked
What a memo asserts about the law.
A memo states things about the law before it argues from them: what a statute requires, what a court held, which rule governs and from when.
Lenz checks each against the published rule and the public record — what the memo asserts, not whether a rule applies to your client.
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Statutes and the rules made under them
“The statute requires X.” “The rule took effect in March.” Lenz looks for the published text and the authority’s own guidance, and returns what it finds, including when it finds too little.
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Case law: verify what a court held
A model can name a real case and misstate its holding. Lenz treats “the court held X” as a factual statement and checks it against the public sources it can reach. When no public record settles a statement, Lenz answers “No Public Record” instead of a score. That doesn’t make the statement false.
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Forms, deadlines, rates and thresholds
The mechanics the example above checks. They turn on the jurisdiction and the tax period, so a memo that names both gives Lenz something to check against; one that leaves them implied does not.
03Before you rely on it
AI tax advice and legal research, before you rely on it.
An assistant’s answer reads the same whether it is right or a year out of date, and the memo drafted from it carries the error forward.
One statement at a time
Lenz checks each statement in the draft against the public record — a regulatory claim, an effective date, a threshold — and reports each one separately.
Hallucinated holdings and legal AI accuracy
A holding a model invented is checked as a statement, not as a citation: the question Lenz answers is whether the case held what the memo says it held.
Regulatory claims in a legal document
What a rule requires, when it took effect, the threshold at which it bites, who it covers: statements with a published answer, each returned with the regulation or guidance it was checked against. Whether the rule reaches your client is analysis, outside the check.
04Where you work
Check the memo in Claude.
Connect Lenz to Claude with one sign-in and no key, and ask for a check before the memo leaves the window: “Check the claims in this memo with Lenz.” Hand over the memo whole; each statement comes back with its own result.
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Extract the statements
The memo goes in whole; each statement comes back with its own result.
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Assess them in bulk
A quick check returns a verdict and a confidence level for each statement, for triaging a long memo.
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Send the uncertain ones to a deep check
The deep check returns the verdict with its sources and the reasoning.
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Route what needs a reviewer to one before delivery
A person reads what is left before the memo goes out.
05In your document
Review the memo in Word.
The S corporation’s federal income tax return is due on April 15March 15.
In the Workbench on a desktop, upload the memo as a Word document (.docx). When the check is done, download the same file with a comment from Lenz on each statement and citation that needs attention, and suggested edits as tracked changes you accept or reject, as a colleague’s review comes back. Lenz does not change the memo’s own text.
A suggested edit comes from Lenz’s checks, not every statement gets one, and a suggested edit is not itself verified: read it, and its sources, before you accept it.
Upload a memo in the Workbench
Private by default. On paid Pro and Scale, zero retention keeps what you submit out of our database.
06Scope
What it checks, and what it doesn’t.
Checks
The factual statements the memo makes, against public sources.
When the memo links a source, Lenz checks that the source says what the sentence claims. A reference with no link and no DOI is not checked.
Doesn’t check
It is not a citator: it won’t tell you whether a case is still good law.
It does not check citation format, authenticate a quotation, or assess the quality of the legal analysis, and it does not judge whether a model wrote the memo.
07Record
A record you can keep.
Open a deep check to inspect the source a statement rests on and to keep the reasoning with the memo: the statement as framed, the verdict and its score, every source named and dated, and the arguments for and against.
Deep check
That record comes from a deep check. Lenz investigates the statement: it researches independent public sources, has models argue both sides on what they say, and returns the verdict with those sources and the reasoning, in about a minute or two per statement.
Quick check
A quick check is the other check: a panel of models returns a verdict and a confidence level in about fifteen seconds, for triaging a long memo. The deep check can change the quick verdict. When it does, rely on the deep check: it is the one that shows its sources and its reasoning.
Warranty
Vendors disclaim accuracy. Lenz warrants the verdict.
A verdict can qualify when a full verification returns True or False with high panel confidence and enough independent sources behind it. Its certificate is a document you can hand to the client with the memo.
On a paid Pro or Scale plan, every full verification that qualifies carries a contractual warranty, at no extra charge.
08Pricing
Try free, no card.
$7.99/ month
500 quick checks or 50 deep checks a month, in any combination.
Or $6.59 a month, billed $79 a year
Choose Plus$99/ month
5,000 quick checks or 500 deep checks a month, in any combination. The warranty on qualifying verdicts.
Or $83 a month, billed $990 a year
Choose Pro$399/ month
20,000 quick checks or 2,000 deep checks a month, for production volumes. The warranty on qualifying verdicts.
Or $333 a month, billed $3,990 a year
Choose Scale09Questions
Published statutes, regulations and the tax authority’s own guidance, plus independent commentary. A deep check includes the sources it used and the reasoning behind the result.
Only what the statement says. Include the jurisdiction and the tax period; Lenz searches public sources for the rule applicable to that statement and returns what it finds.
Lenz searches the public record when it runs the check, so a published change is in scope; every source and the check itself are dated. Where superseded guidance is still online beside the new rule, a deep check returns both sides and the reasoning. Put the tax period or the date in the statement to anchor the check.
What you send through the API or a connector is private to your account, and each adviser’s checks are their own. The example on this page is a memo paragraph Lenz wrote and published. Anthropic, Google, OpenAI, Perplexity and xAI, the AI model providers Lenz uses, do not train their models on what Lenz sends them. By default Lenz keeps your memos and their results while your account exists; on Pro and Scale you can set a shorter period, including zero, where what you submit is never written to Lenz’s database. The model providers keep what their own terms say, listed on the subprocessors page.
Every check you run is private by default, on the website, through the API and in the Claude connector. On a paid Pro or Scale plan you can set zero retention: what you submit is never written to our database, a result stays readable from our cache for 24 hours, and the model and search providers keep what their own terms say.
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