It's literally just filling out the paper forms except in a web interface and it does most of the math for you. And then you can file electronically for free regardless of your income level, and it produces a final PDF with all forms filled out for your files.

It can be tricky to do your taxes the first time around depending on their complexity, but the good thing is that once you figure it out, you just use the previous year's PDF's as a reference for the current year's. The lines move around a little bit year-to-year but it's usually the same idea. And it becomes pretty obvious what has changed (that requires research), and you can figure out if anything has changed in your own financial situation that warrants filling out a new line or new set of forms.

(I don't believe there's anything specifically textfile-based. But this is definitely the electronic version of doing your taxes "manually" with full control.)

[1] https://en.wikipedia.org/wiki/Free_File#Free_File_Fillable_F...

That's interesting. Apparently submits electronically sometimes - but if you need attached statements, for example for f1116, you have to print the product and mail it. Otherwise supports surprisingly MANY forms - many of them with some limitations which are enumerated for you. Some schedules are not included, for example this year f1116 requires 1116 Schedule B for carryovers and that's not provided here. So again if you need f1116 then you'll be printing and mailing that. Really... Many forms are included.

  2017-01-01 open Expenses:GA:Insurance USD
    tax_form: "1040 Schedule C"
    tax_line: "15"
    tax_description: "Insurance (other than health)"

Being able to write comments is also super-useful. A real life example:

  ; We can make a "Section 1.263(a)-1(f) de minimis safe harbor election" to
  ; treat repairs and improvements to tangible property as an expense, which
  ; would otherwise have to be capitalized.  A statement that we are making the
  ; election must be attached to our tax return and should include name, address,
  ; and Taxpayer Identification Number.  Under the election, we must apply the de
  ; minimis safe harbor to all expenditures meeting the criteria for the election
  ; in the taxable year.  The limit is $2,500 per invoice.
  ;
  ; https://www.irs.gov/businesses/small-businesses-self-employed/tangible-property-final-regulations
  2016-01-01 open Expenses:RD:Hosting:Repairs:DeMinimis USD
    tax_form: "1040 Schedule C (R&E)"
    tax_line: "21"
    tax_description: "Repairs and maintenance"

I'm considering whether to move away from it but it would of course be a considerable investment of effort.

A ton of repetitive bookkeeping tasks become so much easier when you can copy and paste, or use keyboard macros or something like multiple-cursors[2], rather than have to click tens or hundreds of times in a GUI. Many years ago I used QuickBooks, and basic tasks like importing a bank statement took at least an order of magnitude longer than they do now.

Having my company's books in Git is also huge when it comes to auditing, concurrency, backups, and figuring out where things went wrong when accounts don't balance. As mentioned in another comment: `git diff` is a really powerful tool and it's awesome to be able to check out the books as they existed at a particular point in time. `git blame` is great for when you're trying to figure out where a number came from. Writing meaningful commit messages and comments keeps me sane when I try to remember a year later why something is recorded the way it is.

The biggest downside—or advantage, depending on how you look at it—is that there's no default or built-in chart of accounts, so you need a certain level of accounting acumen (or professional advice) to set things up at first. I'm pretty sure GnuCash aims to be plug-and-play, whereas Beancount is more akin to a programming library that you use to build an accounting system. I agree with the grandparent commenter, who said that text-based accounting is "the best and most flexible accounting experience I've ever had." But the cost of that flexibility is that there's a fair amount of DIY involved.

[0]: https://beancount.io/

[1]: https://github.com/beancount/beancount-mode

[2]: https://github.com/magnars/multiple-cursors.el

Remapping a transaction to a different tax line item (e.g. if tax law changes, as it did this year with § 174) is just a matter of updating the account metadata. This is much more convenient than having to go back through the books and reassign transactions to different accounts.

It's plain text in Git, so I have the usual tools available. For example, `git diff` can tell me what changed between tax years, and I can check out a copy of my books as they existed at the time a past year's return was filed.

I love the idea, but not being an accounting expert (maybe you are), I'd be afraid that some immaturity or lack of expertise in the software would cause a big problem in a critical way. What makes you confident in it?

Also, how do you share data with accountants, etc.?