I don't ask AI to build my spreadsheets. I ask it to find what's wrong with them. That one change has caught three mistakes in my own household budget that I'd stared at for months without seeing.

A spreadsheet has a particular kind of authority. The numbers line up in tidy columns, the total sits in bold at the bottom, and it all feels like maths that has already been checked. Mostly it hasn't. It has been checked by the person who built it, which is the one person least likely to spot the slip, because they know what they meant.

Why I audit instead of build

When assistants first got good at spreadsheets, I tried the obvious thing: describe a budget and let the AI produce the formulas. It worked, in the sense that something appeared. But I couldn't have told you whether row 14 was right, and I'd have been trusting a sheet I hadn't read and a machine that cannot tell me it is unsure.

So I flipped it. I build the sheet myself, slowly, the way I did before any of this existed. Then, before I rely on a number for anything that matters, I hand a copy to an AI and ask it to behave like a sceptical colleague. Building stays mine. Checking is the part I'm happy to share, because a second set of eyes is exactly what a solo spreadsheet never gets.

The ten-minute check

It's the same every time, and it takes about ten minutes once you've done it twice.

1. Strip it first. I make a copy and replace names, account numbers and anything identifying with placeholders. The sheet only needs to keep its structure and its numbers. If the file belongs to an employer, I stop and check the rules before going any further, which is the point I make in more detail in my guide to using AI at work safely.

2. Ask for questions, not fixes. My prompt is roughly: "Act as a careful reviewer. Look at this spreadsheet and list anything that looks like an error or a risk: formulas that skip rows or ranges, numbers typed over formulas, inconsistent formulas down a column, dates or numbers stored as text, totals that don't match their parts. Don't change anything. Give me cell references." Asking for a list of questions rather than a corrected file matters. A corrected file is another sheet I haven't read.

3. Check each flag myself. Every item gets opened and looked at with my own eyes. Some are real, some are fine, and a couple are the AI misreading my layout. That last part is the reason I never let it make the edits.

4. Ask what I haven't told it. A final prompt: "What assumptions does this sheet make that I should double-check?" It's the least reliable answer of the lot, but it occasionally points at a blind spot, such as a monthly figure I'd entered as if it were weekly.

"The AI isn't smarter than me about my own money. It's just not attached to my sheet, and that turns out to be most of what a reviewer is for."

The three mistakes it found

These are from my own household budget, which I'd have described as accurate.

A total that quietly stopped one row short. I'd added a new utility bill by inserting a row at the very bottom of the block, just outside the range the total was summing. For two months the "total outgoings" figure was lower than reality by one bill. It flagged the range straight away. I'd looked at that cell a dozen times and never counted the rows above it.

A number typed over a formula. In one month, a savings figure that should have calculated from the income and spending above it had been replaced with a plain number I'd typed in during a rushed moment, probably to make something balance. Every cell around it was a formula. That one wasn't. It looked identical on screen, which is precisely why I'd never have found it by eye.

Dates that weren't dates. A few payment dates I'd pasted from a bank statement were stored as text, so they refused to sort and a monthly summary skipped them. The sheet looked fine and was wrong in the way that never announces itself.

The honest verdict: None of these were dramatic, and that's the point. They were small, plausible and invisible, the sort of thing that leaves a figure wrong by £40 for half a year. Ten minutes caught all three. I wouldn't use this for anything legally or financially binding without a human who knows the subject, but for my own numbers it's the cheapest quality check I've added in years.

Where it gets it wrong

It isn't magic, and it's worth being straight about the misses. It sometimes flags things that are deliberate, such as a hard-coded figure I'd typed on purpose because it was a fixed contract price. It has no idea which of my categories matter, and it can't tell me whether my assumptions are sensible, only whether they're consistent. On a long, messy file it can lose the thread and start citing cells that don't say what it claims, which is another reason every flag gets opened and read.

The bigger risk is the one I started with: trusting the output because it sounds confident. If you let the assistant fix things silently, you've simply moved the unchecked step somewhere less visible. Keep the review a list of questions and keep the decisions yours.

Where this fits with the rest of how I work

It sits alongside a few other habits. I'd already moved most of my planning into a plain sheet after running Notion and a spreadsheet side by side for a month, which made a reliable sheet matter more. The same step-by-step logic is behind my AI budgeting guide, and the review prompt above is one of the saved ones in my set of prompts I reuse every week. If you're new to AI and want a gentle way in, the first two modules of Your First 30 Days With AI are free, no card needed. Auditing a spreadsheet is a good first real job to hand it.

And if you want the next honest test as I run it, join the newsletter.

Questions people actually ask

Can AI build a spreadsheet for me instead?

It can draft one, and for a quick tracker that is fine. But a spreadsheet it builds is still one nobody has checked, so the same audit applies. I would rather build the sheet myself, where I understand every formula, and use the AI as a second pair of eyes on the result.

Is it safe to paste my spreadsheet into ChatGPT or Claude?

Only after you strip out anything personal. I replace names, account numbers and employers with placeholders and paste a copy, never the original. If the file belongs to your employer, check your workplace rules first, because pasting company data into a chatbot is a different question from pasting your own budget.

Will AI catch every spreadsheet error?

No. It is good at structural slips such as a sum that skips a row, a number typed over a formula or dates stored as text. It is poor at knowing whether your assumptions are right, and it will sometimes flag something that is fine. Treat its list as questions to check, not a verdict.

Do I need a paid plan to do this?

Not for a household sheet. The free tiers of the main assistants handle a few hundred rows comfortably. Larger files are where paid plans or the built-in spreadsheet assistants start to earn their keep.