I set up my own gōdō kaisha (a Japanese LLC) and have done everything myself since, from the registration paperwork to the monthly books. Even with accounting software open, I kept stalling on which account a transaction belonged to. I started building 一人社長 Solo Boss to cut down on those stalls, and I still use it every month for my company's books and filing prep.
Keep your books where they are
Solo Boss is for one-person companies in Japan that keep their own books and want help only with the year-end close and the filing. Your bookkeeping stays in the software you already use. You import the journal CSV from Yayoi Kaikei, Kaikeiō, freee or Money Forward, plus your opening balances, and then:
- Before you file, it checks the books against more than 30 rules and shows the rows and amounts to fix.
- It builds the balance sheet, the income statement and Schedule 4 (別表四) from the same numbers.
- It writes the filing files for e-Tax and eLTAX. The e-Tax .xtx file loads into the National Tax Agency's e-Tax software (web version).
- Your tax accountant can look at the figures through a link with an expiry date and a password, without making an account.
The two above are the home page, captured 2026-10-15. The check example is fictional data drawn on the page, and the screen under it is from the read-only sample company. You can walk through that sample company without signing up. The two below are inside it.
It got my own filing wrong
The product itself made mistakes. The AI journal assistant split tax-inclusive and tax-exclusive amounts the wrong way. Expense reports added consumption tax on top of amounts that already included it. The consumption-tax return overestimated a refund. I fixed each error I found, and I'm reviewing past returns with my tax accountant.
So I made its role plain. Solo Boss does not file for you. The AI drafts, and you confirm. Anything that needs a judgment call goes to a tax accountant, and that is what I do too.
What it can't do, and what it costs
It can't submit a return from inside the app: you send the file with the e-Tax software. It doesn't support tax audits and doesn't make tax judgments. It shows where each number comes from, but the final check belongs to your tax accountant. It isn't finished, and I build it alone. Its home page also comes in English.
Right now every feature is free. There is no card to register, and payments are switched off. If that changes, I'll say so before it starts. The current plan is to charge only for the filing files: a filing pack at ¥19,800 per business year (tax included, one-off), with the first business year free.
If something looks wrong, or the consumption tax is handled in a way you think is incorrect, tell me. I read every report myself. For your own tax questions, please ask a tax accountant.