How Sole Proprietors in Japan Can Deduct Car Expenses and Home Rent for Business

Hi, my name is Taisei Koshida, and I am a certified public accountant and tax accountant.

I aim to assist non-Japanese business owners who need help with reading or writing in Japanese. If you find the Japanese tax return system challenging, I can help you with your tax filings.

If you are unclear about the expense ratio in Japan, you might find this blog helpful.

Don’t Claim 100% of Expenses

When claiming car expenses or home rent as business expenses in Japan, it is important not to claim 100% unless the asset is used exclusively for business purposes.

If you claim the full amount, there is a high risk that the deduction could be disallowed during a tax audit. In most cases, a portion of these expenses is considered personal and therefore not deductible.

Calculate Your Expense Ratio Reasonably

To prepare for potential tax audits, you should calculate your expense ratio in a reasonable and well-documented manner.

For car-related expenses, the most accurate method is to track business usage based on actual distance, such as recording mileage with an odometer. However, in practice, this may not always be feasible.

As an alternative, using a reasonable usage pattern is acceptable. For example, if the car is used for business on weekdays and for personal use on weekends, you may deduct five-sevenths (5/7) of the total expenses.

Home Rent: Use Space or Time-Based Allocation

For home rent, if one room is used exclusively for business, the deductible portion should be calculated based on the floor space ratio.

In other cases, you may calculate the ratio based on business usage time (e.g., working hours vs. personal use). The key is to apply a reasonable and explainable method that can be supported if questioned by the tax authorities.

Key Takeaway

The most important point is to apply a reasonable and consistent allocation method. This will help you justify your deductions and reduce the risk of issues during a tax audit in Japan.

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