How much refund are you leaving unclaimed?

An AI tax-shield tracker and 確定申告 (annual tax return) self-prep service for individual rental-property owners in Japan. You photograph or upload any property document; AI classifies it, extracts the figures, and files it to your property; and your projected tax refund recomputes on the spot. You can also ask plain-language questions about your own records — "How much did I spend on repairs this year?" — and get answers grounded in your documents.

In February, the year's records become the filing-ready year-end report that matches your status: the 青色申告決算書 for blue-return filers, or the 収支内訳書 for white filers. First-year owners get told how and when to file the blue-return application (青色申告承認申請書) so the better treatment kicks in as early as possible.

It's the standard real-estate-income computation: rental income minus deductible expenses minus depreciation. For a leveraged single rental that result is very often negative — and in Japan, that loss offsets your salary income (損益通算), so the projected refund is roughly the deductible loss times your marginal tax rate, plus a separately shown reduction in next year's residence tax. One statutory carve-out — loan interest on the land portion of your purchase can't offset salary income — is computed, not glossed over.

The projection is always shown as a band (say, ¥180,000–¥210,000), never a promise. It's an estimate of a filing outcome, not the filing outcome. Missing months or ambiguous expenses widen the band, and the app tells you what capturing them would be worth. If your rental turns a profit, it projects the additional tax owed instead — better seen in July than discovered in March.

All documents and extracted data are encrypted at rest and never used to train third-party models. Tenant-identifiable information is hidden behind a per-property toggle that defaults to off. Every extracted number carries an audit trail back to its source document. When you delete your account, all data — including tax documents — is deleted within 30 days.

Preparing someone else's tax documents as a business is restricted to licensed 税理士 (tax accountants) — and SmartPropFact doesn't do that. It's self-preparation software, the same legal category as Japan's mainstream tax tools: you prepare your own return using it. SmartPropFact never signs a return, never submits one, and never represents you before the tax office. The built-in Q&A answers questions about your own recorded data and general public tax rules; it doesn't give individualized tax advice. If you want professional judgment, hire a 税理士 — SmartPropFact's exports are designed to make that engagement shorter and cheaper.

Stated plainly: the English interface ships within a few months of launch — document reading is bilingual from day one, but until then the app UI itself is Japanese. There's no e-Tax direct filing — you get a filing-ready PDF and CSV to attach to the return you file yourself. Non-resident owners are out of scope (the tax-agent 納税管理人 / 20.42% withholding regime is a genuinely different product). And there are no B2B features yet.