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Ten mistakes AI makes reading invoices and documents when nobody checks
You can ask any AI to do this. If nobody checks it, chances are it made at least one of these mistakes.
And you probably won’t see it. Every mistake below looks right: the rows are neat, the columns line up, the totals often add up, and the AI tells you, with confidence, that the spreadsheet is done.
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 add a column the way a calculator does. When it can’t read something, it doesn’t leave a gap. It fills in something that fits. So a wrong spreadsheet 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.
Mistakes AI can make when nobody checks
The most common and hardest to spot come first.
1. It makes up a figure so the invoice adds up
When a number is hard to read, AI fills in the one that makes the total come out right. The invoice adds up perfectly. The number just isn’t on the page.
2. It misreads a digit on a scan or a photo
An 8 becomes a 3, a 1 becomes a 7, and a decimal point disappears under a stamp or a fold. $1,234.50 turns into $123,450, and nothing on the screen looks wrong.
3. It skips a page and says nothing
A sideways photo, a faint second page or the back of a receipt is left out. The spreadsheet looks complete. Your total is short, and nothing tells you why.
4. It adds when it should subtract, or the reverse
A discount, a credit note or a deposit already paid gets added to the total instead of taken off. A credit note becomes a bill, and the money you’re owed shows as money you owe.
5. A total doesn’t add up all its rows
The total at the bottom is a formula, so it looks trustworthy. But it adds rows 5 to 40 when the invoices run to row 41, or it adds the Tax column when it should add the Total column. The figure looks right, and it’s wrong.
6. It counts an invoice twice, or merges two into one
The same bill sent once as a scan and once as an email is counted twice. Three invoices scanned into one PDF come out as one. A two-page invoice comes out as two.
7. It swaps the quantity and the price
“2 hrs @ $65” becomes 65 hours at $2. The line total is still $130, so the invoice still adds up. Only the page tells you it’s wrong.
8. It guesses whether a bill was paid
“Thank you for your business” is read as paid. A total is marked as owed when the page says it was paid in cash. Your list of what you still owe is wrong in both directions.
9. It takes the wrong name, number or date
The fax machine’s header becomes the vendor, or your own company does. A check number or your account number becomes the invoice number, and 04/03 becomes April 3 when the page meant 4 March.
10. It adds euros to dollars
Invoices in different currencies are added into one total without converting them, as if €50 were $50. The grand total is a number that means nothing.
What to do about it
You can catch most of these yourself if you check the spreadsheet against the documents, not against the AI. The checks are in How to check an AI-made invoice spreadsheet. It takes time, and it has to be done every time.
Or let us do it. Our own proprietary software checks every workbook against your documents, and it is built to catch mistakes like these before the workbook reaches you. Anything that can’t be read clearly is asked about, never guessed (how we check).