Fact-check an AI-drafted tax or legal memo.
Lenz is a fact-checking service for tax and legal memos. It identifies 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 citation checker; what it does not do has its own section below.
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.”
Full verification
- An S corporation files its federal income tax return on Internal Revenue Service Form 1120. False high confidence 1/10 irs.govuscode.house.govturbotax.intuit.com+2 more S corporations generally file their federal returns on Form 1120-S, not Form 1120. IRS materials explicitly identify Form 1120-S as the “U.S. Income Tax Return for an S Corporation,” while plain Form 1120 is a distinct return generally associated with C corporations. Omitting the “-S” changes the form being identified and makes the statement incorrect.
- An S corporation has an April 15 federal income tax return filing deadline. Mostly False high confidence 3/10 uscode.house.govgovinfo.govecfr.gov+14 more The standard deadline stated in the claim is incorrect for calendar-year S corporations. Federal law generally requires an S corporation to file by the 15th day of the third month after its tax year ends—normally March 15 for a calendar-year filer. April 15 can apply to an S corporation with a January 31 fiscal-year end, but that narrow exception does not justify the unqualified statement.
- A calendar-year C corporation files its federal income tax return on Form 1120. True high confidence 9/10 irs.govthomsonreuters.comfreshbooks.com+3 more
- A calendar-year C corporation’s federal income tax return is due on April 15. True high 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. True high confidence 9/10 ecfr.govirs.govuscode.house.gov+10 more
Checked 2 September 2026. Open a row for the sources it used and the reasoning that weighed them.
What a memo asserts about the law.
A memo states things about the law before it argues from them: what a statute or a regulation requires, what a court held, which rule governs a situation and from when, and the filing specifics that follow. Lenz checks those statements against the published rule and the public record, and returns a result for each. It checks what the memo asserts; it does not decide whether a rule applies to your client.
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.
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 Lenz finds no public evidence for a statement, the finding says so and the result scores low. Treat that statement as unverified.
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.
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 in a confident register. Lenz checks the statements in the draft against the public record — a regulatory claim in a compliance note, an effective date in a contract, a threshold in a filing — and reports each one separately, so you see which parts of the advice have something behind them.
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 and who it covers: those are statements with a published answer, and each comes back with the regulation or the guidance it was checked against. Whether the rule reaches your client is analysis, and outside the check.
In Claude, Cursor or a script.
Connect Lenz to the assistant that drafts the memo (Claude: one sign-in; Cursor and Claude Code: one command with your key) and ask for a check before the memo leaves the window. Hand over the memo whole: Lenz pulls out the factual statements it can check, so you are not marking them up by hand, and each one comes back with its own result.
Memos a product generates, checked before delivery
When the memos are the product — a service or a tool that drafts them for clients — the check belongs in the pipeline rather than in someone’s habit. A script or the API sends each memo as it is drafted, pulls the statements out, assesses them in bulk, sends the uncertain ones to a full verification, and routes what needs a reviewer to one before the memo is delivered. Same sequence on every memo, at whatever volume you draft them.
What this does not do.
It does not validate a list of citations, 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. It checks the factual statements the memo makes, against public sources.
A record you can keep.
Open a full verification 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.
That record comes from a full verification: Lenz searches independent public sources for the statement, weighs what they say and returns the verdict with those sources and the reasoning, in about 90 seconds per statement. An assessment is the other check, a judgement rather than an investigation: a panel of models returns a result and a confidence level in about 10 seconds, which is how you triage a long memo before deciding what to verify.
Pricing
Free tier, no card: 100 assessments or 10 full verifications a month, in any combination. Developer is $99 a month for 5,000 assessments or 500 full verifications, the same way, and Scale is $399 a month for production volumes. Every plan includes 1,000 extractions a day, an extraction being one call however long the text.
Frequently asked questions
Published statutes, regulations and the tax authority’s own guidance, plus independent commentary. A full verification 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 at the moment it runs the check, so a change that has been published is in scope. Every source comes back with its date and the check itself is dated. Where superseded guidance is still online beside the new rule, a full verification returns the sources on both sides and the reasoning that weighed them, rather than picking one quietly. Put the tax period or the date in the statement and the check is anchored to it.
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.