Finance and accounting decision
JapanFinance.tools
A competent developer can build the calculators and questionnaire, but the product’s ongoing value depends on authoritative, kept-up-to-date tax rules and trust—things a single developer can approximate but not fully replicate for high-stakes users.
Visit website↗Built by François Rejeté, who ships 6 products in this index
Not priced
No pricing page we fetched carried a figure, so there is nothing to compare against. The build side is still real.
$100one-off120 h to build
$0/mo3 h/mo upkeep
No published price to break even against.
No open-source build does this yet
Nothing published replaces this one, so a replacement starts from an empty file. Here is what it would have to cover.
What a replacement has to do
- User answers residency and asset questions → calculator applies Japan-specific gift/inheritance formulas → shows tax estimate and explanatory guidance
What it still won’t have
- Ongoing legal/tax updates and jurisdictional maintenance
- Brand trust and recognized authority when advising high-stakes cases
- The author’s curated explanatory content and phrasing tailored for foreigners
- Linked social/professional presence and referrals
What remains hard
- Product polish and ongoing maintenance
First-year cost
No published price
JapanFinance.tools does not publish a price we could read, so there is nothing to compare against. What building costs is below.
Money you would actually spend
Time you would spend
—
What you would spend
What we assumed
The verdict above measures whether you could build it. This one is only about money.
Runnable build prompt
Build a small web app (Next.js + React frontend, Node/Express backend, PostgreSQL) that reproduces JapanFinance.tools' core: 1) a short residency/tax-liability questionnaire with server-side validation; 2) an inheritance tax calculator implementing Japan residency rules, allowances and progressive rates; 3) a gift tax calculator with shared tax-rule module; 4) English-first UI with expandable explanatory text and printable/PDF export; 5) session persistence and basic input validation. Out of scope: professional tax advice, automated filings, and multi-jurisdiction tax engines. Include unit tests for calculator logic, end-to-end tests for questionnaire flows, error handling for invalid inputs, and CI deployment scripts.
How we checked
How the score was reached
- Partly verdict base52
- 5 cited sources+3
- Evidence score55
The base comes from the verdict. Everything under it is a check that either happened or did not, and each one is a fact frozen in this record rather than a judgement made at render time - so the same evidence always produces the same number.
How scoring works →Cited sources · 5
Every page the run actually retrieved.
- official productJapanFinance.tools homepage — features list
- official productJapanFinance.tools homepage — features list
- official productJapanFinance.tools homepage — features list
- official productJapanFinance.tools homepage — marketing
- official productJapanFinance.tools homepage — audience
Integrity checks
What held up, and what did not.
