Common Mistakes in Tax Return Filing in Japan

Mistake	Correct Information	Impact
Failure to report all income	All income (salary, side jobs, real estate, cryptocurrency, etc.) must be properly declared	If underreporting is discovered, additional tax penalties may apply
Overstating deductible expenses	Only expenses directly related to the business are deductible	If disallowed in a tax audit, additional taxes and penalties may apply
Claiming both Furusato Nozei One-Stop Exemption and filing a tax return	If filing a tax return, Furusato Nozei should be reported within the return, not separately	The One-Stop Exemption becomes invalid
Miscalculating medical expense deductions	Health checkups and cosmetic treatments are not deductible. Insurance reimbursements must be deducted from eligible expenses	The deductible amount may be reduced
Forgetting to claim the first-year housing loan deduction	The housing loan deduction requires a tax return in the first year	Missing the claim results in financial loss
Errors in spousal or dependent deductions	The income of the spouse or dependent must be correctly calculated and meet eligibility criteria	Over-claimed deductions may be questioned by the tax office
Submitting an e-Tax return but failing to complete the process	Ensure the submission is successfully completed and check for the confirmation email	An incomplete submission may be treated as a failure to file, leading to penalties
Expecting a quick refund	Refund processing typically takes 1 to 1.5 months	Delayed refunds may cause unnecessary worry
Believing that missing the filing deadline is not a problem	Late filings may result in penalties such as additional tax or late payment fees	Unnecessary tax burdens may arise
Relying entirely on a tax accountant	The taxpayer is ultimately responsible for the accuracy of the tax return	Any errors could result in penalties for the taxpayer

And non resident can ask to refund too much withholing tax from your salary. You'd better consult your employer!