> If you're acting in good faith and your accountant does something crazy or evil, your liability is limited to some extent.

From my understanding, you are the person signing off on the paperwork that is submitted to the IRS.

There is this cache 22 with taxes.

You are responsible, but you outsource it to a accountant. Because you are not knowledgeable about the taxes. But you are expected to be knowledgeable to understand the tax documents that you submit to the IRS. That is why the accountant always ask you to review the documents and sign them like 20 times.

The same applies when you run a company, depending on the country, you need to prove yourself knowledgeable in accounting, before you are allowed to run a company. Normally that is included in a university degree, but if you have a middle school diploma, you need to do a official examen to get that degree.

Whatever you submit for your company, you are again responsible. Even if you hired a accountant.

So while technically, if a accountant makes gross mistakes, the bill will always fall in your lap, because you are expected to understand the reports you submit to the IRS. And catch any errors before doing so.

With the IRS, the burden of proving your innocents is often put you. Its because the good faith argument can be misused easily. That is why the buck stops at you.

So using a LLM or a accountant, really does not matter. Sure, a accountant can go to jail if there has been major issues (its not going to be with one client issue).

But you can lose your house / company, have your life ruined by whatever you submitted.

“A computer can never be held accountable, therefore a computer must never make a management decision.”

– IBM Training Manual, 1979

https://simonwillison.net/2025/Feb/3/a-computer-can-never-be...

I agree with you on every point but it is interesting to see real world benchmarks like this. Showing the standard benchmarks that all LLMs use is not only boring but at this point likely gamed or even has issues (according to OpenAI) by every LLM.

1 Just as with traditional non-ai ways of doing things, there is a deterministic layer that can trigger when things are off. This can range from letting the ai know to stopping before a human confirms.

2 Usually, specially for SMBs, nobody goes to prison over accounting errors. That's because SMB owners make mistakes all the time and, because of that, authorities are fairly practiced in understanding how mistakes look, and how fraud looks.

Sure! In classic accounting firms you'd typically have one accountant doing the books and then the other reviewing the first accountant's work. Given the model's accuracy (and models will only get better), only by automating the "doing" and keeping a human to do the review part we will already shave huge amount of time and costs without risking the compliance part.

The LLM is, after all, trained on a world with a lot of tax fraud in it.

It’s almost impossible to be in a situation where your taxes end up this wrong you’re accused of fraud. I honestly do not believe my accountant does anything better than AI or AI generated code that does calculations to see what you should be paying.

> This is a prime example of a problem space where accuracy matters, but it also matters who ultimately goes to prison.

I don't disagree that tax fraud is bad but accuracy really doesn't matter 1/10th what people think it does.

Something to keep in mind in the EU with VAT is that there are approximations, errors and then huge frauds like the infamous "carousel fraud". Sadly the carousel fraud is all too common in the EU: this one gets people really sent to jail. But it's not an error a LLM shall make that could lead to a carousel fraud taking place: it's an elaborate scheme.

Now... If you're self-employed and have to pay the VAT (which may or may not be the case depending of the type of self-employment work you do) or if you're a SME and you've got approximations and errors well it's really not a big deal.

Because the public servants in charge of collecting the VAT and verifying that you filled your stuff correctly... Do make shitload of errors too. And then, depending on the country, these public servants have a special privilege: they can decide an amount of VAT+fine (if there's a fine) that you agree with and if you agree with it, their number is the number.

It's everything but a correct number. It's a number they ended up on that is "close enough" (for some definition of "close"). Sometimes by hammering number after number on a little calculator and then ending up saying:

"We ask you to pay 3500 EUR of additional VAT. If you sign here and accept, the IRS (equivalent of the IRS) won't be able to bother you ever again for that year/years".

This notion that, somehow, there's "one" correct number and that public servants paid something like 2 K EUR net per month (which may be the reason why so many are so prompt to ask for bribes btw) can determine it in a few minutes is ridiculous.

It's simply not happening. Usually the accountant doesn't know the exact number. The SME owner doesn't know the real amount of VAT due. And the public servant(s) in charge of a VAT audit, if any takes place, certainly as zero clue as to what the exact VAT number should be.

The rules are way too complicated, there are way too many special cases, and some things are simply extremely hard to take into account (for example during one audit the person told me he disagree with the 90% of 21% VAT deducted for my ISDN line --yup it was a long time ago-- but then I told him it was during a previous TVA audit, a few years before, that the VAT auditor, seen my job, fixed at 90%).

For some stuff you can opt for a fixed number: say a car, there are rules, depending on the country, where you can, say, get back 75% of 50% of the VAT. But people can also, depending on the country, opt-in for the "real usage": you do 12 387 km during the years, how many were really for work? 6 287 km ? Or may 6 275 km?

What if one day while going to work, you took a detour because you want to drop a gift for your grandma's birthday? How were these kilometers accounted for?

Restaurant bills? What if one of the person wasn't work related (your nephew happened to be in town and you had to take car of him and you knew the clients well so they didn't mind: how does the accountant account for that)?

Gifts to client. You got a discount buying 6 packs of bottle of champagne, but not five (no discount if only five), so you bought a sixth one. But that sixth one you kept for you.

Nobody computes those amounts correctly. Nobody.

And don't get me started on the public servants who'll give, during an audit, an unfair advantage to people from their community (whatever that community may be) or those, literally, banging underneath the table while talking about their next vacations: they're telling you an "arrangement" can be made. Basically you give that one person some money (cash bills of course) and, boom, the 20 K EUR of VAT you had to pay suddenly gets lowered down to 5 K EUR.

You refuse? It'd be too bad if those 20 K became 25 K EUR wouldn't it? Mafia-style.

This is all happening. Don't tell me it's not happening because I know people on both sides of these "trades".

Depending on the EU country, it can even be the norm.

As rational people who like determinism (at least I do), at first glance it looks like a SME's accounting is something square but it really ain't. Or let's put it this way: it there's one number that is the really the amount of VAT the SME has to legally pay, I'd guesstimate 0.01% of the SMEs out there pay, to the cent, the proper amount.

All this to say: the approximations, hallucinations and errors of LLMs in accounting for VAT are probably just on par for the course.

P.S: ah yup... The boss (say major airline company) giving a business card and its PIN code and asks to take good care of the clients: and an employee takes them to strip clubs, they all get drunk like crazy, and explodes the expenses on the business card. Way, way, way more than what is OK to put into expenses to entertain clients. Well guess what: I know for a fact this happens too. And I know for a fact this ain't accounted for properly either.