"How often do tax audits actually happen?" The answer is in the statistics. Field audits of individuals number about 48,000 a year — less than 1% of all filers. But they are not random: you are "selected" to be audited through data analysis. And when one does come, the additional tax averages ¥1.35 million per case. Based on the National Tax Agency's published statistics, this article explains the probability of an audit, the mechanism by which people are selected, the flow on the day, and how to prepare properly — without scaremongering and without hiding anything.
① Income tax audits and contacts total about 600,000 a year. Of these, full-scale field audits number about 48,000, less than 1% against the 23 million-plus filing taxpayers[National Tax Agency (in Japanese)].
② However, the additional tax per field audit (special and general) averages ¥1.35 million. People are selected on the premise that "if we come, we will very likely find something."
③ Selection is done by data analysis using the KSK system plus source information (payment records, invoices, platform reports, etc.). Low gross margin compared with peers, an abnormal expense ratio, or a mismatch between filings and deposit records are triggers.
④ The National Tax Agency itself has published that its priority targets are non-filers, overseas assets, crypto assets, and online transactions.
⑤ The right preparation is to "keep books and supporting documents you can explain." That alone means an audit is nothing to fear.
The real picture of the odds: low, but "not random"
| Category | Number of cases (AY Reiwa 5) | Meaning |
|---|---|---|
| Field audits (individuals, income tax) | About 48,000 | Full-scale audits where an examiner visits. Less than 1% of filers |
| Simple contacts (documents, phone, requests to visit the office) | About 550,000 | "Inquiry" letters and the like. These are much more common |
| Total additional tax | ¥139.8 billion | Averages ¥1.35 million per field audit (special and general)[National Tax Agency (in Japanese)] |
The gut feeling that "for an individual, one might come once in a lifetime, if that" is statistically correct; on the other hand, when one does come, the rate of findings (discrepancies) is high. In other words, the tax authorities narrow down "suspicious filings" by data before they come. The field-audit rate for corporations is higher than for individuals (on the order of a few percent), and roughly "once every several years to ten years" is the practical sense.
How you get "selected"
- The KSK (National Tax Agency Comprehensive Management) system: It centrally manages nationwide filing and payment data plus source information, and analyzes filing content by comparison with the same industry and same scale. Outliers are extracted.
- The source information cross-checked against you: payment records submitted by your business partners, withholding slips, invoice registration and transaction data, inquiries to banks, transaction reports from platforms (flea-market apps, gig work), and from overseas, account information under the CRS (Common Reporting Standard). Your sales can be grasped through the other party's records even before you file.
- Characteristics of filings that are easily selected (from statistics and practice): continually keeping sales just below thresholds such as ¥10 million or ¥2.9 million / an expense ratio that stands out against peers / a cash business / several years of profit since opening with no audit ever / being a non-filer in the first place (published as a priority issue[National Tax Agency (in Japanese)]) / large deposits from crypto assets, overseas transactions, or online sales.
What happens if one comes? (the flow and mindset)
- Prior notice: In a voluntary audit, in principle you receive notice by phone of the date and the tax items covered (for cash businesses and the like, an unannounced visit is also possible). The schedule can be adjusted, and if you have a retained tax accountant it goes through the accountant.
- On the day (usually 1–2 days): an interview about your business overview → checking of books, receipts, and passbooks. Answer the facts to what you are asked; for anything vague, you don't have to answer on the spot — "I will check and get back to you" is fine.
- The result: ① filing approved (no problem) ② a recommendation to file an amended return (if you accept the findings, amend and pay penalty tax) ③ correction (if you cannot accept it, you have the right to file an objection).
- What you must not do: discarding, falsifying, or making false statements about documents. These lead directly to heavy additional tax (35–40%) and revocation of blue-return status, and are treated in a completely different way from a mere calculation error.
Note that only a tax accountant can be entrusted with handling an audit (tax representation). For complex cases or where large findings are expected, it can be worth engaging one even just for that phase (Do you need a tax accountant?).
The right preparation = keeping yourself in an "explainable" state
- Keep books and supporting documents (receipts, invoices, passbooks) for the required period (electronic transactions must be stored as data).
- For gray-area expenses, keep the basis for apportionment and the description (10 gray zones of expenses).
- Cross-check sales against deposit-based records so there are zero omissions. The heaviest issue in an audit is not the denial of expense apportionment but the exclusion of sales.
- If you notice a past error, file an amended or late return voluntarily without waiting for an audit (the penalty is greatly reduced. Guide to recovering from non-filing).
FAQ
What is the probability that a sole proprietor gets a tax audit?
In the National Tax Agency's AY Reiwa 5 statistics, income tax field audits number about 48,000 — less than 1% against the filing taxpayers (23 million-plus). But because selection is not random sampling and is done by data analysis, it concentrates on people whose filings contain outliers and on non-filers.
From what sales level does an audit become more likely?
No clear threshold amount is published. Rather than the amount itself, "outliers compared with peers" and "a mismatch with source information" are the triggers. Filings where sales continually line up just below the consumption tax threshold (¥10 million) are known as a typical target of analysis.
I received notice of an audit. Can I refuse?
Even in a voluntary audit there is a duty to comply, and you cannot refuse without a legitimate reason (there are penalties). However, the schedule can be adjusted. The realistic response is to get your books in order and, if necessary, engage a tax accountant for tax representation.
How many years back can they examine?
Usually 3 years; 5 years if there is a discrepancy; and up to 7 years where there is fraud such as disguise or concealment. Once heavy additional tax applies, the burden jumps sharply.
Data sources
- Number of audits, additional tax, ¥1.35 million per case, priority issues (non-filing, etc.): National Tax Agency, Status of Income Tax and Consumption Tax Audits, etc. for Administrative Year Reiwa 5 (in Japanese) (PDF (in Japanese))
- Corporation tax audit results: National Tax Agency, Overview of Corporation Tax Audit Results for Administrative Year Reiwa 5 (in Japanese)
* This article explains the system and statistics and does not show how to avoid an audit. For individual matters, please consult a tax office or a tax accountant.