The tax office calls and says: "We would like to check some points in your return — if there is an error, please file an amended return." Is that a tax audit? The answer is: sometimes yes, sometimes no. And which one it is decides whether the penalty tax is zero or over a hundred thousand yen — same call, same amended return. The National Tax Agency states publicly that its officers "shall inform the taxpayer, before entering into the specific procedure, which of the two it is." So you may ask.
The situation
An unknown landline number calls your business mobile in the early afternoon. The caller gives the name of a tax office, their own name and section, and continues:
"There are a few points we would like to check regarding last year's return. We would like to ask about the timing of your sales recognition — could you look at your records, and if there appears to be an error, submit an amended return?"
The tone is calm; no visit is proposed. Checking the books afterwards, you find sales recognised in the wrong period. Should you file as asked — or has an "audit" just begun?
This is the most common form of contact from a tax office. In the FY2024 administrative year there were 689,000 "simple contacts" for income tax (by phone or letter), up 23% from 558,000 the previous year. Field audits that year numbered 47,000 — fifteen times fewer.
What the rules say
The National Tax Agency addresses exactly this in Question 2 of its FAQ on tax audit procedures — a question revised in July 2026.
An audit examines the content of a return through the inspection power, for the purpose of determining a specific taxpayer's tax base or tax amount.
Separately, as administrative guidance, the authorities may ask a taxpayer to review their return voluntarily — and, if needed, to submit an amended return voluntarily — where the return appears to contain calculation errors, transcription errors, omissions or misapplications of law.
Being asked by phone to amend does not automatically make it an audit. Administrative guidance is a distinct category of contact.
"Where a taxpayer voluntarily submits an amended return on the basis of such administrative guidance, delinquency tax may be payable, but the additional tax for understatement is not imposed (if the original return was filed late, the additional tax for failure to file is imposed, in principle at 5%)."
"Officers shall inform the taxpayer, before entering into the specific procedure, whether it is an audit or administrative guidance."
Verdict
Asking is neither rude nor uncooperative. The agency publishes that officers inform you before starting the procedure, so it is something you should be told without asking. If you were not told, confirming is the correct step.
Source: National Tax Agency FAQ on tax audit procedures (for general taxpayers), Q2
If it is guidance, filing voluntarily means no additional tax for understatement — speed pays. If it is advance notice of an audit, the calculus differs: filing without checking closes off points you might have contested. Establish which it is first.
Correcting voluntarily at the guidance stage costs no penalty; letting it escalate into an audit does. Ignoring it is the most expensive option.
How the numbers change
Suppose you filed on time and an extra ¥1,000,000 of income tax later falls due (original tax liability ¥300,000).
following guidance¥0
before anticipating correction¥75,000
／by correction¥125,000
| When you file | Additional tax for understatement original filed on time | Additional tax for failure to file original late or absent |
|---|---|---|
| Voluntarily, following guidance | none | 5% in principle |
| Voluntarily, before advance notice | none | 5% |
| After notice, before anticipating correction | 5% 10% on the excess | 10% up to ¥500k／15% ¥500k–¥3m／25% above |
| After the audit, or by correction | 10% 15% on the excess | 15% up to ¥500k／20% ¥500k–¥3m／30% above |
For 2023 income years onward, failing to produce books when asked during an audit, or recording less than half the sales that should have been recorded, adds 10% to the additional tax (5% if less than two-thirds). Repeat non-filing in the two preceding years adds a further 10%.
Even with no additional tax, paying late means delinquency tax. For 2026 the rate is 2.8% a year for the first two months after the due date and 9.1% thereafter. File and pay close together.
The order to work through on the call
- Identify the caller. Note the office, section, name and number — then call back on a number you looked up yourself, not the one you were given. Impersonation scams exist.
- Ask whether this is an audit or administrative guidance. You should be told anyway. Write down the answer.
- If it is an audit, record the advance notice. The tax items, periods, purpose, start date and place are notified (Article 74-9).
- If it is guidance, ask exactly what to review. The scope should be narrow and specific.
- Do not conclude on the call. "I will check my records and come back to you" is a complete answer. You need not admit an error over the phone.
FAQ
Q. The tax office asked me by phone to file an amended return. Is that an audit?
A. It may be, or it may be administrative guidance. The agency explains that it may ask taxpayers to review their return voluntarily where it appears to contain calculation errors, transcription errors, omissions or misapplications of law. Officers are to state which it is before starting the procedure, so if you were not told, ask.
Q. Does amending under guidance mean no penalty?
A. The additional tax for understatement is not imposed. Delinquency tax may still be payable, and if the original return was late the additional tax for failure to file applies, in principle at 5%. Only the understatement penalty disappears.
Q. Will asking make me look suspicious?
A. The agency publishes that officers shall inform the taxpayer, before entering into the specific procedure, which of the two it is. It is something you should be told without asking, so confirming is a legitimate step.
Q. Is there any point in amending after receiving advance notice of an audit?
A. Yes. Filing after notice but before anticipating a correction gives 5% (10% on the amount exceeding the greater of the original tax liability and ¥500,000), against 10% (15% on the excess) once the audit has run. Moving early still reduces the cost.
Sources
This article is general information. Whether an additional tax applies depends on the facts. Consult a tax office or a licensed tax accountant.