Legal Landscape for Side Jobs in Japan
Many Japanese companies have traditionally prohibited or restricted side employment in their work rules. However, since 2020, government policy has shifted toward promoting side jobs.
Enforceability of Side-Job Prohibitions in Work Rules
Baseline: Freedom of Occupation (Constitution, Article 22)
Employees have freedom to choose their occupation. Employers generally cannot restrict activities outside working hours.
Permissible Exceptions (Requiring Justification)
Courts (e.g., Tokyo District Court, March 13, 1986, Manna Transport case) have upheld prohibitions in specific circumstances:
| Valid Prohibition | Example |
|---|---|
| Impairs work performance | Excessive side-job hours affecting main job |
| Competitive relationship | Working for a direct competitor |
| Reputational / confidential harm | Side job damaging company image |
| Information leakage risk | Side job creating secret information risk |
Blanket prohibitions without specific justification tend to be invalid.
MHLW 2020 Revised Guidelines
The Ministry of Health, Labour and Welfare revised its guidelines in 2020, indicating that side employment should be accepted in principle.
Key points: - Prohibitions/restrictions require rational justification - Approval systems must have clear standards - The Model Work Rules were revised to default to allowing side employment
Aggregation of Working Hours (Labor Standards Act Article 38)
Aggregation Rule
Working hours across multiple employers are aggregated (Article 38(1)).
If the combined total exceeds statutory limits (8 hours/day, 40 hours/week), overtime pay obligations arise.
Practical Management
| Item | Content |
|---|---|
| Starting point | The company that hired first is the baseline |
| Overtime pay burden | The secondary employer (side job) pays overtime premium |
| Management method | Employee self-reporting is common |
The 2020 guideline revision introduced a "management model" (pre-setting side-job hours) to reduce the employer's administrative burden.
Dual Social Insurance Enrollment
Enrollment Threshold
If a side job meets the following conditions, health insurance and employee pension enrollment is required at the secondary employer too:
- Scheduled working hours ≥ 20 hours/week
- Monthly wage ≥ ¥88,000 (expanded since October 2022)
- Projected employment exceeding 2 months
- Not a student
Dual Enrollment Procedure
When enrolled at both employers, submit a "selection of primary insurer / multi-employer declaration" to the pension office. Premiums are apportioned between employers by standard monthly remuneration ratio.
Post-Termination Non-Compete Obligations
Non-Compete During Employment
During employment, competitive conduct is prohibited as part of the duty of good faith (even without an express clause).
Post-Termination Non-Compete Agreements
After leaving, employees are generally free to compete unless they have signed a specific non-compete agreement.
Courts assess reasonableness based on (Tokyo District Court, etc.):
| Factor | Reasonable Range |
|---|---|
| Duration | 1–2 years (3+ years is high risk) |
| Geographic scope | Business area / actual competition zone |
| Industry/role | Limited to specific functions/roles |
| Compensation | Non-compete allowance or enhanced severance |
Non-compete agreements without compensation are likely to be held invalid (Tokyo District Court, August 30, 2002, etc.).
Summary
Side employment is now policy-favored in Japan. Blanket prohibitions are hard to justify and risky; implementing a rational approval system is the practical solution. Dual social insurance enrollment and working-hours aggregation require administrative systems. Post-termination non-compete clauses are enforceable if narrowly scoped and accompanied by adequate compensation.