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Twelve mistakes AI makes in lease abstracts when nobody checks
You can ask any AI to abstract your leases. If nobody checks the abstracts against the leases, they can carry any of these mistakes.
And nothing on the abstract will show it. Every mistake below looks right: every box is filled in, the dates are dates, the rents are rents, and the AI tells you, with confidence, that the abstract is done.
Finding them takes real work. A lease with its amendments, riders and side letters can run to a hundred pages or more, and a building can have dozens of leases. Every term on the abstract has to be found on its page, as the latest amendment left it. By hand, that can take hours for each lease.
Why these mistakes are so hard to find
A chat AI writes the answer that seems most likely. It doesn’t go back to the page to look again, and it doesn’t hold each amendment against the terms it changed. When a lease doesn’t say something, it doesn’t leave the box empty. It fills in what leases usually say. So a wrong abstract and a right one look exactly the same, and asking the AI to double-check itself doesn’t help: it checks with the same eyes that made the mistake.
And once a lease is abstracted, the abstract is what everyone works from. The rent roll, the underwriting, the lender’s file and the critical-dates calendar are built from it, so one wrong term is wrong everywhere at once. At a 6% cap rate, every $1,000 a year of rent the abstract overstates adds about $16,700 to what the property seems to be worth.
Mistakes AI can make when nobody checks
The most common and hardest to spot come first.
1. It reads the lease as signed, not as amended
The second amendment cut the rent by 15% to keep the tenant, and moved the expiration to 2029. The AI abstracts the lease it read first. Every figure on the abstract is right for a lease that no longer exists, and every report built on it carries the old rent forward.
2. It applies the amendments in the wrong order
The files aren’t named in date order. The AI applies the 2024 amendment, then the 2021 one, and the older rent overwrites the newer one. The abstract names a real amendment beside the rent, so it looks right.
3. It fills in a term the lease doesn’t have
The lease has no renewal option. The abstract shows “one five-year option at fair market rent,” because leases like it usually have one. Nothing on the abstract says it was assumed.
4. It writes a fixed renewal rent as “market”
The lease gives two five-year renewals at $28 a foot. The abstract says “at fair market rent.” If the market is at $40, the tenant will renew at $28. On 20,000 square feet, that’s $240,000 a year the abstract leads you to count on and the lease doesn’t give you.
5. It leaves out a right that sits in a rider or a side letter
The tenant’s right to leave after year five is in a side letter, at the end of a long file. The abstract shows a ten-year lease with no early termination. On a $40,000-a-month tenant, that’s $2.4 million of rent the leases don’t promise you.
6. It works out a notice date from the wrong day
Renewal notice is due “not less than twelve nor more than fifteen months before the expiration,” and an amendment extended the term by three years. Counted from the old expiration, the window lands three years early, and the calendar can show it closed when it is still to come. A tenant who exercises inside a window you didn’t know about holds you to the option.
7. It gets a rent step wrong
The lease’s table steps the rent up every January. The AI works the 3% steps out itself instead of copying the table, rounds each one its own way, and drops a step. One missed step of $1,400 a month is $16,800 a year, and about $280,000 of value at a 6% cap rate.
8. It quotes words the lease doesn’t say
The “lease language” beside each term reads like a quote, but it’s the AI’s summary, written to sound like a lease. Or the section and page it cites say something else. You can’t check a term against words that aren’t on the page.
9. It misreads a scanned page
On a scanned amendment, $8,250 is read as $6,250, or 2031 as 2021. The figure looks like any other, and the AI doesn’t say the page was hard to read.
10. It mixes up the parties
The guarantor’s name ends up as the tenant’s, or the owner who sold the building stays on the abstract as the landlord. A notice sent to the wrong party, or to an address an amendment replaced, may not count as notice at all.
11. It keeps the old area or the old base year
The amendment that added 2,400 square feet set a new base year of 2024 for the new space. The abstract shows the old area and one base year of 2021. Every expense bill built on it is wrong: either the tenant is over-billed and can claim it back on audit, or the owner gives away every dollar the costs rose in between.
12. It doesn’t tell you a document is missing
The third amendment refers to a second amendment dated March 3, 2020, which isn’t in the files. The AI abstracts what it has and says nothing. Whatever the second amendment changed is missing from the abstract, and nothing on it says so.
What to do about it
You can catch most of these yourself if you check the abstract against the lease and every amendment, not by asking the AI. The checks are in How to check an AI-made lease abstract.
Or let us do it. Our lease abstracts are checked by our own proprietary software before they reach you. It checks every term and every figure against the lease’s own words on its page, checks that every amendment’s changes are on the abstract, and works every date out again from the lease’s words. Each term comes with the document, page and section it comes from. Anything your documents don’t say is asked about, never guessed, and an amendment, rider or addendum a lease refers to that you didn’t send is asked for by name.