Eleven days after the tax office called to announce an audit — and three days before the audit itself — the taxpayer filed five years of overdue returns. "Filed before the audit began, so the non-filing penalty should be reduced." Japan's National Tax Tribunal said no. What the ruling's timeline revealed: during the years the taxpayer assumed nobody knew, a desk investigation had been quietly under way for three years. This instalment reads how the timing of a late return changes the penalty — and when it no longer can.
The case: five unfiled years of side income
A company employee earned referral fees on the side for five years and never filed a return on them. On 13 May the tax office phoned: an on-site audit would be held on 27 May to confirm his tax obligations.
He engaged a tax accountant and filed five years of overdue returns on 24 May — three days before the audit.
The office assessed the non-filing penalty at the unreduced rate, holding the returns were filed "in anticipation of an assessment based on an investigation". He appealed, arguing the filing was voluntary because the on-site audit had not yet begun. The Tribunal dismissed the appeal.
The timeline: the investigation began three years earlier
- 3 years before
The tax office audited the company paying the fees and learned of the payments — then interviewed the taxpayer himself about the arrangement.
- Weeks later
Contracts and bank-account details were forwarded to his local tax office.
- 1 year before
The local office queried his bank and confirmed the deposits.
- Early May
Filing records checked: five years, nothing filed. Employer's withholding slips reviewed.
- 13 May
Advance notice call. Asked "any income besides salary?", he admitted the fees and was asked to prepare records.
- 24 May
Five years of returns filed through a tax accountant, three days before the audit.
- 27 May
On-site audit. The penalty followed at the full rate.
Three years passed between his name surfacing and the phone call. Silence from the tax office does not mean ignorance.
"Before the audit" was not enough
His anchor was an NTA administrative guideline: a return filed at the stage when only the audit date has been arranged is, "as a rule", not treated as filed in anticipation of assessment. The Tribunal answered on two levels. First, "investigation" includes desk work — collecting records, querying banks, checking filing histories — not just the on-site visit; by the notice date the office already had near-certain grounds to assess. Second, the guideline states a rule of thumb only; the statute requires a case-by-case weighing of the investigation's progress, the taxpayer's awareness, and how the filing came about. Having been interviewed three years earlier and questioned about side income during the notice call, he filed knowing an assessment was coming — no reduction.
The three tiers of Japan's non-filing penalty
| When you file | Penalty |
|---|---|
| Before any audit notice, voluntarily | 5% |
| After audit notice, before anticipation of assessment | 10% (15% above ¥500k; 25% above ¥3m) |
| After anticipation (audit under way) | 15% (20% above ¥500k; 30% above ¥3m) |
On a hypothetical ¥3 million of back tax (¥600k × 5 years), that is roughly ¥150k / ¥310k / ¥460k — before late-payment interest, and before the 40% heavy penalty if concealment is found. The middle tier is not guaranteed: as this ruling shows, a last-minute filing can be pushed to the top tier by the totality of circumstances. Only filing before the notice is certain to be cheap.
What to take away
| Common belief | Reality |
|---|---|
| "Filing before the on-site audit counts as voluntary" | Desk investigation counts as "investigation", and anticipation can be found from the totality |
| "The guideline says so" | Guidelines state principles; individual facts override them — this ruling is the proof |
| "No contact = not on their radar" | Three years passed between detection and the call |
| "An audit at my client doesn't concern me" | Payer audits collect who-was-paid-what records, which are forwarded to your tax office |
FAQ
Q. When must a salaried employee file for side income?
A. When side income (after expenses) exceeds ¥200,000 a year, an income tax return is required. Below that, resident tax must still be declared.
Q. How far back does non-filing reach?
A. Five years as a rule, seven where deception is found. Waiting only accrues late-payment interest.
Summary
- A late filing for five years' worth of returns, submitted 11 days after advance notice and three days before the on-site audit, got no reduction — the full non-filing penalty applied (ruling dated October 15, Reiwa 7 / 2025).
- The tax office had already learned of the income three years earlier through an investigation of a business partner, and had even completed bank inquiries and checks of filing history.
- The term "investigation" was ruled to include the tax office's internal desk review, and the administrative guidelines were judged to be merely a general principle, not binding.
- The non-filing penalty is 5% for voluntary filing before contact, 10% after audit notice but before detection is likely, and 15% after detection is likely.
- The lower rate is guaranteed only before an audit contact arrives. If you have unreported income, file a late return now.
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Sources
The case is a ruling anonymised and published by the National Tax Tribunal. Rulings are outside copyright under Article 13(iii) of the Copyright Act; the Tribunal's site follows the Public Data License (v1.0).