Starting a Side Job as an Employee in Japan: Employer Rules, Contracts and Tax Filing

Check the employer’s procedure first

Read the outside-work provisions in your work rules and employment contract. Identify whether you must notify the employer or obtain permission, where to submit information and when you may start. Ask HR if the requirements are unclear; submitting a form does not guarantee approval.

MHLW guidance recognizes employees’ freedom outside working hours while discussing restrictions involving work performance, confidential information, competition and the employer’s reputation. A formal breach of a rule does not automatically settle whether disciplinary action is valid. Check your circumstances with the relevant parties. MHLW: Side-job guidance booklet (Japanese).

Separate employment from freelance work

A “side job” can use either arrangement. Japan’s Freelance Act covers qualifying business-to-business outsourcing, with obligations depending on the parties and, for some rules, the duration. Do not assume identical payment or termination rules apply to every project. JFTC: Japan’s Freelance Act (Japanese).

Manage time and company information

Where the Labor Standards Act’s working-time regulations apply to multiple employment relationships, working hours must be combined across employers. Cooperate with their management by reporting planned and actual hours. This does not mean every independent contracting hour is legally aggregated in the same way. MHLW: Combined working hours across employers (Japanese).

For freelance work, still record total time to protect rest and assess the impact on your main job. Do not reuse the employer’s devices, internal documents, customer lists or work products without authorization. Check competition and conflicts even when using public materials. Weekend scheduling is covered in Weekend-Only Side Jobs in Japan: Check Weekday Contact, Revisions and Rest (Japanese).

Understand what the ¥200,000 test counts

For the cases below, salary payments are subject to withholding. The test differs according to the number of salary sources; it cannot be applied by deducting personal work costs from every side-job payment. NTA: When employees must file an income-tax return (Japanese).

Other requirements exist, including annual salary receipts exceeding ¥20 million. The NTA also describes an exception for multiple salaries where total salary receipts after certain income deductions are ¥1.5 million or less and applicable non-salary, non-retirement income is ¥200,000 or less. That deduction calculation excludes casualty losses, medical expenses, donations and the basic deduction. Some income is excluded from the test, including certain separately taxed amounts. Read the full official conditions before deciding.

If you file for a refund, such as to claim a medical-expense deduction, generally include small amounts of applicable income too. This does not turn legally non-taxable receipts into taxable income. NTA: Income that should not be omitted from a tax return (Japanese).

A fictional example: revenue and salary differ

A has one year-end-adjusted salary, freelance revenue of ¥300,000, allowable expenses of ¥120,000 and no other applicable income. The freelance income is ¥180,000. A must still check other filing requirements and resident tax. If A files for a medical-expense deduction, that ¥180,000 generally belongs in the return.

B receives ¥250,000 in additional salary that was not year-end adjusted. For the multiple-salary test, those salary receipts count. B cannot simply subtract communication costs to reproduce A’s ¥180,000 figure. Income classification and allowable expenses depend on the facts.

Check resident tax separately

A resident-tax declaration may be needed even when no income-tax return is required. Filing an income-tax return normally removes the need for a separate resident-tax declaration. Consult the municipality where you lived on January 1. Yokohama City: Resident tax (Japanese).

Collection also differs for salary and non-salary income. Shibuya’s fiscal-2026 rules collect resident tax on salary, including additional salary, through the main employer. The employer’s notice does not list income details, but choosing personal payment cannot guarantee secrecy. This is a municipal example, not a nationwide change date. Shibuya City: Salary resident-tax collection from fiscal 2026 (Japanese).

Prepare an application and a record sheet

Fictional outside-work application

Work: articles based on public sources, under freelance contracts

Schedule: three hours Saturday and two Sunday; state weekday contact availability separately

Controls: no company documents, customer information or devices

Busy periods: reduce commissions and check the employer’s required disclosures

Keep salary records by employer and freelance sales and allowable expenses by activity. Retain invoices and receipts; distinguish fees from actual deposits. Record preparation, meetings and revisions as well as production. Recheck contract conditions before starting and tax requirements for the relevant year. Select a first project whose scope and communication schedule you can explain.

Related guides

• Balancing Remote Employment and Side Work in Japan: Time, Devices and Contract Checks (Japanese)
• Remote Part-Time Employment in Japan: Finding Jobs and Checking Terms (Japanese)
• Weekend-Only Side Jobs in Japan: Check Weekday Contact, Revisions and Rest (Japanese)

Sources and further checks

Public information checked on October 5, 2026. These sources concern Japan; verify the conditions that apply to your case.

• MHLW: Side-job guidance booklet (Japanese)
• MHLW: Combined working hours across employers (Japanese)
• JFTC: Japan’s Freelance Act (Japanese)
• NTA: When employees must file an income-tax return (Japanese)
• NTA: Income that should not be omitted from a tax return (Japanese)
• Yokohama City: Resident tax (Japanese)
• Shibuya City: Salary resident-tax collection from fiscal 2026 (Japanese)

The related Otame4 guides linked above are in Japanese.