Amended Return or Claim for Correction? Five Years Back

This is a translation of the Japanese original. The Japanese version is authoritative; figures follow Japanese tax law.

It happens often enough: you file your tax return and only afterwards notice that you left out the medical expense deduction, never entered your furusato nozei donations, or missed one payment of side-job income. There are two ways to put it right, and which one you use depends on the direction of the error: a "claim for correction" (kosei no seikyu) if you paid too much tax, an "amended return" if you declared too little. A claim for correction can be made within five years of the statutory filing deadline, and if it is accepted the tax comes back to you. An amended return filed on your own initiative, before the tax office contacts you about an audit, carries no understatement penalty - only late payment interest. Employees who never filed a return at all do not use a claim for correction: they file a "refund return" for up to five past years. This article sets out a case-by-case table of procedures, deadlines and penalties, and how to prepare the paperwork in the National Tax Agency's online return preparation corner, based on NTA materials.

The short answer: a table by case

What you noticed	If you filed a tax return	Employee with only a year-end adjustment (no return filed)	Deadline and penalty
Left out the medical expense deduction or the self-medication tax scheme	Claim for correction	Refund return	Five years from the statutory filing deadline for each year (for a refund return, five years from 1 January of the following year). No penalty
Forgot to enter furusato nozei (the donation deduction)	Claim for correction	Refund return (not needed if the one-stop exception is still valid)	Same as above
Left out the dependent, spousal, single-parent or disability deduction	Claim for correction	Refund return	Same as above
Forgot to submit the certificates for iDeCo, life insurance, earthquake insurance or social insurance premiums	Claim for correction	Refund return	Same as above
Forgot the first-year filing for the housing loan deduction	—	Refund return (first year only; from the second year the company's year-end adjustment handles it)	Same as above
Missed expenses, or counted the same sales twice (you overpaid)	Claim for correction	—	Same as above. Prove it with your books and receipts
Forgot to declare side-job, real estate or dividend income (you underpaid)	Amended return	Late return (where a return was required in the first place)	No understatement penalty if you file voluntarily before the advance notice of an audit (a late return carries a 5% failure-to-file penalty). Late payment interest runs from the day after the payment due date
Claimed more in deductions than you were entitled to (you underpaid)	Amended return	—	Same as above
You noticed inside the filing period (by 15 March)	Corrected return - simply file the right return again		No penalty. The return filed later is the one that counts

Sources: National Tax Agency, Tax Answer No.2026 "When you have made a mistake on your tax return"[NTA], No.2024 "When you have forgotten to file a tax return"[NTA], No.2030 "Refund returns"[NTA]

Claim for correction: recovering an overpayment up to five years back

The NTA states that "where the tax to be paid was too much, or the tax to be refunded was too little, you may receive a refund of tax by submitting a claim for correction to the head of the tax office", and sets the deadline as "in principle within five years of the statutory filing deadline"[NTA]. As of October 2026, that reaches back to the 2020 tax year, whose filing deadline was 15 April 2021.

Gather the evidence. Medical receipts, donation receipts, documents showing the situation of your dependants, deduction certificates - anything that shows the deduction is real. A claim for correction is expected to come with "documents proving the facts underlying the grounds for the claim".
Prepare the "claim for correction / amended return" in the NTA's online return preparation corner. You enter the contents of the original return, change the parts that were wrong, and the refund from the difference is calculated automatically. Past tax years are supported too. Send it through e-Tax, or print it and take it to the tax office.
Wait for the tax office to examine it. If the claim is accepted, a "notice of correction" arrives and the refund is paid into your account. This normally takes two to three months. Refund interest runs from the day after the filing deadline and is added to the refund.
Resident tax follows automatically. The correction of your income tax is notified to your municipality, and your resident tax is reduced as well, then refunded or offset. If your income tax was zero to begin with and only your resident tax was overpaid, you file a separate claim for correction (a resident tax return) with your municipality.

A forgotten furusato nozei entry most often arises from the accident where the one-stop exception is voided by filing a tax return, and a claim for correction gets it back. For what counts as a medical expense and how the deduction is calculated, see how to calculate the medical expense deduction.

Employees with only a year-end adjustment: a refund return for five years

Someone who has never filed has no "original return" to correct, so instead of a claim for correction they file a refund return - an ordinary tax return. A refund return can be filed for five years from 1 January of the year following the tax year, which means you can claim five years of forgotten medical expense deductions, furusato nozei and dependent deductions in one go. You prepare one return per year in the preparation corner. You need the withholding tax statement from that year; if you no longer have it, ask the company to reissue it.

Example: an employee (20% tax bracket) who left out the dependent deduction for a parent aged 70 living with them (580,000 yen) for three years

Income tax: 580,000 yen × 10% = 58,000 yen × 3 years = 174,000 yen (plus the special income tax for reconstruction)
Resident tax: 450,000 yen × 10% = 45,000 yen × 3 years = 135,000 yen
A total of about 310,000 yen comes back (the resident tax side follows automatically from the refund return and is reduced or refunded by the municipality)

This is the case for people who gained a dependant after the year-end adjustment, got married, or started supporting a parent but forgot to tell the company. For who qualifies as a dependant, see the complete guide to the dependent deduction.

Amended return: declare the shortfall yourself and there is no additional penalty

Where income went undeclared or you claimed deductions you were not entitled to, and the tax came out too low, you file an amended return. There are two penalties, and the timing changes them dramatically.

When the amended return is filed	Understatement penalty	Late payment interest
Voluntarily, before the advance notice of a tax audit	None	Yes (from the day after the statutory payment due date to the day of payment)
After the advance notice, but before the audit points it out	5% (10% on the part exceeding the larger of the tax on the original return and 500,000 yen)	Yes
After the audit has pointed it out	10% (15% on the same excess)	Yes
Where there was disguise or concealment	Heavy additional tax of 35% (in place of the penalty above)	Yes

Late payment interest runs at a rate in the 2% range a year for the first two months after the payment due date, and in the 8% range a year thereafter (the exact rates are set each year by the special standard rate). If you pay at the same time as filing the amended return, the tax office does the calculation and notifies you later. The only real defence is to file as soon as you notice: the longer it sits until an audit finds it, the higher the penalty climbs. For how side-job income should be handled, see filing a tax return for a side job.

If there are years when you filed nothing at all, that is a "late return". The failure-to-file penalty is 5% if you file voluntarily (waived if you file within one month of the statutory deadline and have paid the tax in full), and 15% or more once an audit has begun. For getting back on your feet after several unfiled years, see coming back from having filed nothing.

Points people get wrong

"Claim for correction" and "amended return" point in opposite directions. A claim for correction gets money back; an amended return pays more in. If a single return contains errors of both kinds, you use one procedure for the net result: a claim for correction if the tax falls overall, an amended return if it rises.
Some choices cannot be revisited. The choice between the medical expense deduction and the self-medication tax scheme, and the choice between aggregate taxation and separate self-assessment taxation for dividends, cannot be changed by a claim for correction once the return has been filed.
The five years run from the "statutory filing deadline". For the 2020 tax year the deadline was 15 April 2021 (extended because of COVID-19), so the claim had to be made by 15 April 2026. The deadline differs by tax year, so check the oldest years first.
Refund interest is miscellaneous income. The interest added to tax returned through a claim for correction (refund interest) counts as miscellaneous income for the following year. It is usually a few hundred to a few thousand yen, but if you are required to file, do not forget it.
Deductions that affect only resident tax go to the municipality. If your income tax was zero to begin with (low income, living on a pension) and you left out a resident tax deduction, you file the resident tax return (claim for correction) with your municipality, not with the tax office.

Frequently asked questions

Does filing a claim for correction make a tax audit more likely?

A claim for correction is a legitimate right, and the claim itself does not trigger an audit. The tax office does examine what you claim, however, so a claim with thin evidence may not be accepted. Put together the documents that show the deduction is real - medical receipts, deduction certificates and the like - before you file.

I cannot pay the extra tax from an amended return all at once.

File the amended return first. Whether the additional penalty applies is decided by the timing of the filing, and a late payment does not increase it (late payment interest does accrue by the day). If payment is genuinely difficult, ask the tax office about a "grace period for tax payment"; instalments and a reduction of late payment interest are sometimes granted.

If the company got the year-end adjustment wrong and I paid too much tax, do I file the claim for correction myself?

The company can redo the year-end adjustment until 31 January of the following year; after that, you file a refund return yourself (or a claim for correction if you had filed a tax return). You do not need the company's help - your own filing gets the money back. You enter the figures from the withholding tax statement as they are and add the deduction that was missing.

Summary

If you overpaid, file a request for reassessment; if you underpaid, file an amended return. A request for reassessment must be made within 5 years of the statutory filing deadline.
For an employee who only had year-end adjustment, it is a refund filing, not a request for reassessment, and it can be done for 5 years from January 1 of the following year.
An amended return filed voluntarily before advance notice of a tax audit carries no penalty for underreporting, though late-payment interest still applies.
If you notice the issue within the filing deadline (by March 15), simply refile as an amended return.
The choice between the medical expense deduction and the self-medication tax system, or between comprehensive taxation and separate self-assessment taxation for dividends, cannot be changed afterward.

Reference links (sources)

This article is based on the materials below. Because the rates of additional tax and late payment interest differ by year, please confirm the actual amount from the notice sent by the tax office.

Note: this article is general information. For an individual decision, check with the tax office or a certified public tax accountant.