[kstrauser]

Boy, do I have bad news for you.

Edit: To be clear, as a sibling post said, the basic arithmetic is easy enough. It's the tax opinion stuff that is absolutely not deterministic. If your situation is even moderately complex, there's a vast number of ways to describe your deductions, each with different tax implications and multi-year requirements. I'm not talking about being Jeff Bezos, either. Is your spouse an independent contractor? Do you own a home? Do you have stock options? Do you have a home office? These alone are enough to make some pretty creative reporting situations.

[crowcroft]

I think it's a very common misconception among programmers that the law is a sort of natural language 'program' where you can consistently deduce that x input generate y output.

[amiga386]

Not to detract from your point, but the French tax system is defined as code.

https://rmonat.fr/talk/impots_gallium19/

[kstrauser]

It sort of is, except that the entire law isn't defined in one place. "Hey, do I have a home office?" Well, "home" is defined over in this regulation, and "home office" is defined over there in that other regulation, and "having a home office" would normally mean this except for this case law that says it can also mean that when these other circumstances apply, and...

These things are knowable, but unless you've spent some time studying it intensely, it's certain that you only know a fraction of the places where the program is written.

If it's helpful, programmers should imagine that it's written in C. At a glance you can tell what something's doing, but once you study it you can find UB all over the place and suddenly it's hard to say what the right answer is until you know the intricacies of the compiler and the target platform. You can't really determine the exact behavior without all that information that lives outside the code. Now, once you have all that, you can surely reason through it all. But how many people actually know all that, or even realize which parts they don't know?

"This is pretty straightforward" is a sure sign of someone who doesn't actually understand it well.

[jcranmer]

Trying to treat law as code-in-English-form is going to lead you horribly astray, however.

The behavior of C code is something that we can, in principle, reduce to semantics in a formal model we know how to describe the behavior of. Now, there's some issues getting there--the specification is more ambiguous than we'd like, and there's definitely certain behaviors that are very challenging to incorporate in a formal model (say, signal handlers). But even something like UB is something that we have good, well-understand models of what exactly it means to hit UB. At the end of the day, whether or not C code is correct, whether or not the compiler is correctly compiling the C code, is a question that has a clearly objective answer.

Law doesn't work like that. Laws are written and interpreted with the understanding that there is flexibility in the mater. If you compute the law and get an absurd result, then people are going to shrug and throw out the absurd result; rather different it is to a compiler where the absurdity is accepted as correct. As a result, there's not really an objective answer to whether or not something is legal, to understanding what will happen in a legal case, like there is to code.

[philipallstar]

> Law doesn't work like that

This is partly because the law predates compilers and modern communication. Why should a crime get different sentences? Often because judges are humans and somehow that makes it okay to lock some people up for years longer than others.

[tptacek]

No it isn't, at least not in common law systems like the US. It is part of the principle of how statutes are drafted that they will be interpreted by human judges and shaped by precedent. It's not a technological limitation.

[jcranmer]

Your example is somewhat apropos because one of the more algorithmic portions of law is sentencing. Since the 1980s (i.e., after the development of compilers!), the US has enacted guidelines for sentencing (see https://en.wikipedia.org/wiki/United_States_Federal_Sentenci...) that allows anyone to read the criminal complaint and compute the expected sentence via a calculator (e.g., https://www.sentencing.us/).

And yet the sentencing guidelines are not binding on outcomes, in part because of the necessary flexibility in law. Sometimes you crunch the numbers and you get absurd results (SBF's fraud conviction is a good example I ran through myself), and so you need the flexibility to throw the algorithm out when the algorithm produces wrong results.

[nerdsniper]

> except that the entire law isn't defined in one place

> These things are knowable

There are absolutely undefined, unknowable areas of law that are waiting on future SCOTUS decisions to be defined.

Heck, we can’t even rely on past SCOTUS decisions.

Even in extremely well-defined law like whether LEO’s have valid PC to search someone during a traffic stop, two different judges in the same district will disagree and appeals courts / state supreme courts can rule quite inconsistently.

That’s by definition not just undefined behavior but also non-deterministic results.

[kstrauser]

I agree. I just mean, you can pretty well know today's state, at least hypothetically. But you better be watching tomorrow's legal news to see if anything important changed.

[dchftcs]

Someone has to be in the news first, and then you learn about it. To that someone, the change you see in tomorrow's legal news is today, was yesterday. It's more a gamble than you think, you just don't feel it until it bites you.

[kstrauser]

FWIW, we're in complete agreement. I stand by mt original statement that these things are nearly impossible for a layperson to be competent in. It's hard enough for people who do it every day for a living. An equivalent would be non-techies saying "I'm not going to pay a software engineer. Just tell the computer what you want it to do!" And that might sound reasonable to other non-techies, while you and I roll our eyes and laugh. I'm sure CPAs and tax attorneys and the like think the same when they hear engineers talk about filing their own non-trivial taxes.

[hnfong]

Well, to put it precisely, an omniscient being would theoretically be capable of knowing today's state of the law with probabilities assigned to the results.

I'm serious. Pick any non-trivial issues of law, ask a world leading expert, and you'd very quickly hear the word "probably" somewhere. Less often than "it depends", but you'll hear those words often nonetheless.

If that's "knowable" to you, I guess it's knowable.

[cyclopeanutopia]

What's a SCOTUS?

[kaikai]

Supreme Court of the US

[wahern]

> [US] tax law drafting style follows default logic, a non-monotonic logic that is hard to encode in languages with first-order logic (FOL).

https://arxiv.org/pdf/2011.07966.pdf

Most law generally is non-monotonic. (See https://en.wikipedia.org/wiki/Non-monotonic_logic) The French tax code is one of the few exceptions.

[jorisw]

A point echoed by Nilay Patel (who used to be a law professional) here https://www.theverge.com/podcast/917029/software-brain-ai-ba...

[gamblor956]

Is your spouse an independent contractor? Do you own a home? Do you have stock options? Do you have a home office? These alone are enough to make some pretty creative reporting situations.

Those questions all have discrete answers, including the much-misunderstood home office. The correct tax outcomes are very much deterministic, in the sense that the same inputs always result in the same outputs. It's simply that there are a lot of options to change the inputs (for example, choosing FIFO vs LIFO for stock sales, using an S-corp vs a sole proprietorship for a personal business).

For example, the home office deduction is only available to individuals who have a home office that is used exclusively for their individual business, not as an employee for someone else's business (the only exception being for flow-through entities where the taxpayer is a shareholder/partner). The "exclusive use" is meant in the all-or-nothing sense. Use your office computer after hours for games? The home office deduction no longer applies. Uses the office space to store personal documents, or really any other activity except for the business activity? The HOD no longer applies. Don't have any income from that business activity you claim are doing in the home office? The HOD no longer applies.

It's simply that enforcement is not deterministic, so people think they get away with a lot of positions that do not survive actual audits. Talk to an IRS agent that handles audits and you'll learn that a failed home office deduction claim is the #2 adjustment to the tax returns of white collar professionals.[1] At a relatively recent tax mixer, IRS agents from the Los Angeles branch office could only recall about a dozen cases in which the home office deduction actually survived an audit, out of thousands, and those taxpayers were extremely rigorous about following the rules to the letter (to the extent that all of them locked their home offices when they were not being used for work).

[1] The #1 reason for adjustments to the tax returns of white collar professionals is attempting to claim business expense deductions without matching business income to deduct against. Technically, the home office deduction is one of these deductions, which is why it is #2 and not #1.

[s1artibartfast]

There are also a lot of non-deterministinc choices one can make. Things like carry forward losses or gains, that no algorithm could know. They depend on your personal plans for the future. You can make specific filing choices that have massive consequences on your future. There are choices like 83(b) elections that can save you tens of millions of dollars a decade in the future, contingent on the events after you file.

[gamblor956]

Those are deterministic choices...

Deterministic means that the results are not random, not that they are known at the time of the initial choice.

[s1artibartfast]

This seems like splitting hairs. The outcome are not known or calcuable.

I suppose a dice roll or the motions of a butterfly are deterministic as well, if you have a full model capable of fully modeling the world.

[mk12]

And there are basic things that shouldn’t be subjective at all but that the IRS refuses to give a clear answer to, like if/how the SALT cap affects deduction for NIIT. There are at least 3 possible interpretations and no consensus.

[jmalicki]

That's because it's law, and the IRS doesn't get to decide that, courts do.

There are parts of the tax code that mean different things in different parts of the US because of conflicting circuit court decisions that haven't made it to the Supreme Court.

[BobbyTables2]

I know my own taxes pretty well. I don’t follow the tax code changes but could fill out a 1040 form on my own. Even did for a short time.

I use tax prep software because I do NOT want to worry whether I copied the amount from line C to line K correctly. The IRS forms are a nightmare!

The postscript in PDF should allow something more sane than what we have today in IRS forms, but that’s just wishful thinking.

[kstrauser]

I use to think that. I'm capable of putting numbers in a form correctly. A good tax preparer can point out things like "did you know that your specific commuting pattern entitles you to claim mileage?", or "the law says the way you have your working environment set up at home means you can deduct some of your utility bills", and so on ad infinitum.

Basically, unless you get someone who has a deep knowledge of the law, if your tax situation is non-trivial (see my post above this) then you might be leaving money on the table. It's a terrible, idea to evade taxes. It's a fantastic idea to realize when you're paying more than you're legally required to so that you can fix it.

[LamaOfRuin]

The IRS's fillable forms do a perfectly fine job of copying values around and doing the basic arithmetic that they can automate.

[Loudergood]

No, that's Intuit lobbying.

[groundzeros2015]

Taxes are not objective. No software can reach into your life and classify your activies into legal categories.

[groundzeros2015]

That’s a true side fact, but that has nothing to do with how the software behaves once you input your answers.