[Summary]
One thing that is easy to get confused about when working as a sole proprietor or having a side job is how much you can deduct as expenses. Expenses are directly linked to tax savings, but that doesn't mean you can include just about anything.
The basis of an expense is whether the expense was directly necessary to generate business income. You need to think of a way to rationally divide the things you use in your personal life into the proportions you use for work.
In this article, we will organize the points that beginners should check first in the order in which they are most likely to stumble in practice. Since taxes vary depending on individual circumstances, please confirm the final decision with an official or specialized contact such as the National Tax Agency, local government, tax office, or tax accountant.
First, the conclusion
The basis of an expense is whether the expense was directly necessary to generate business income. You need to think of a way to rationally divide the things you use in your personal life into the proportions you use for work.
| Check points | way of seeing |
|---|---|
| Things that can easily become expenses | Purchasing, outsourcing costs, work software, communication costs for business use, transportation costs, materials costs, etc. |
| things that require attention | Expenses that need to be apportioned for housework, such as rent, smartphone costs, electricity costs, and vehicle costs. |
| Things that are unlikely to become expenses | Personal eating and drinking, hobbies, family travel, living expenses, etc. |
| evidence | Keep receipts, invoices, credit card details, and notes of purpose of use. |
The important thing when reading tax articles is not just memorizing the system name. It's about looking at your income, accounts, deductions, and reporting methods separately.
common misconceptions
- If you have receipts, I think it's all expenses.
- There is no basis for apportioning housework.
- Even expenses unrelated to sales are included.
This is an area where it is easy to get confused just by reading the search article. In particular, "sales" and "income," "income tax" and "resident tax," and "NISA" and "taxable account" need to be treated as different things.
Order of actual checking
If you are confused, it will be easier to organize if you check them in the following order.
- Can you explain the relationship with your business?
- Did you separate your personal and work parts?
- Did you save your receipts and statements?
- Are you recording it monthly?
If it is still difficult to make a decision after looking at the above, it is safer not to leave it to your own judgment. Please check through official channels such as consultation with the tax office, the National Tax Agency's tax return preparation corner, and consultation with a tax accountant.
Summary
The more expenses you have, the better; it is important to be able to explain them. If you keep a record that allows you to see the relationship with your work later on, it will make filing your tax return much easier.
While it's hard to get away with not knowing about taxes, there's no need to fear them too much if you sort them out early. When your income increases, when you start investing, or when you want to use deductions, it is most practical to prepare your records early rather than at the end of the year.
Source/reference materials
- National Tax Agency, No.2210 Easy knowledge of necessary expenses
- Confirmation date: 2026-05-30