Medical Evidence Requirements in Incapacity Cases — Japan

In Japanese employment law, medical evidence becomes particularly important when an employee claims that illness, injury, mental-health conditions, or disability prevents them from performing their contractual duties, or when an employer considers leave, return to work, reassignment, or dismissal.

There is no single statutory rule requiring one particular type of medical certificate in every incapacity case. The evidentiary requirements depend on the issue being decided: sickness absence, return to work, fitness for a particular job, occupational injury, or dismissal for inability to perform work.

The central legal framework is Article 16 of the Labour Contract Act: a dismissal lacking objectively reasonable grounds and social acceptability is invalid. MHLW guidance likewise explains that dismissal because of inability to provide labour can sometimes be legitimate, but dismissal may be invalid where recovery is expected or reasonable dismissal-avoidance measures such as leave were not considered.

1. What Is “Medical Evidence” in an Incapacity Case?

Medical evidence can include:

1. Doctor's medical certificate (診断書 / shindansho)
2. Diagnosis and clinical findings
3. Expected duration of incapacity
4. Functional limitations
5. Treatment history
6. Prognosis
7. Whether the employee can perform the particular job
8. Whether restrictions or accommodations are possible
9. Occupational physician's opinion
10. Specialist medical opinion
11. Results of employer-requested medical examinations
12. Industrial accident medical records
13. Workers' compensation decisions
14. Medical evidence concerning causation
15. Evidence concerning fitness to return to work.

The crucial distinction is between:

“The employee has a medical condition”

and:

“Because of that condition, the employee cannot perform the essential duties of this particular employment.”

The second proposition generally requires more than merely proving a diagnosis.

2. Medical Diagnosis Alone Is Not Always Enough

Suppose an employee produces a certificate stating:

“The employee suffers from depression.”

That establishes medical information, but it may not answer the employment question.

The employer or court may need to know:

• Can the employee attend regularly?
• Can the employee work eight hours?
• Can the employee perform the essential functions?
• Can the employee work with restrictions?
• Can the employee perform another suitable role?
• How long is the incapacity expected to last?
• Is return to work realistically foreseeable?
• Is a gradual return possible?

Japanese MHLW guidance specifically discusses situations where an employee returning after mental-health leave provides a doctor's certificate confirming fitness for work. It also recognizes that employers may have legitimate reasons to seek occupational-physician or designated-specialist evaluation where doubts remain about fitness for return.

3. Article 16 of the Labour Contract Act

Article 16 provides the general rule governing dismissal:

A dismissal that lacks objectively reasonable grounds and is not considered socially acceptable is invalid.

Therefore, where dismissal is based on incapacity, the employer should be able to demonstrate a factual basis for concluding that:

1. the employee cannot adequately perform the job;
2. the incapacity is sufficiently serious;
3. the situation is not merely temporary where continued employment is reasonably feasible;
4. appropriate leave or rehabilitation measures have been considered where relevant;
5. reassignment or alternative duties have been considered where appropriate; and
6. dismissal is proportionate to the circumstances.

MHLW's employment guidance expressly identifies inability to provide labour because of personal injury or sickness as potentially reasonable grounds, while noting that courts have rejected dismissal in circumstances including expected quick recovery or failure to consider measures such as leave.

4. Medical Evidence for Sickness Leave

An employer may establish through its work rules that employees must submit medical documentation when requesting extended sickness leave.

A medical certificate may identify:

• disease/injury;
• commencement date;
• expected absence period;
• treatment requirements;
• whether work is contraindicated;
• expected date for reassessment.

However, HR should avoid demanding unnecessarily detailed medical information.

The employer normally needs information necessary to determine employment capability, rather than unrestricted access to the employee's entire medical history.

5. Medical Evidence for Return to Work

Return-to-work cases are particularly important.

The employee may submit a doctor's certificate stating:

“Fit to return to work.”

But the employer may legitimately need to determine whether the employee can actually perform the relevant job.

MHLW's guidance specifically states that an employee returning from illness-related leave should generally demonstrate that they are capable of working, commonly through a medical certificate from the treating physician. It also notes the possibility of occupational-physician or designated-specialist assessment where the employer has concerns about the treating physician's opinion.

A proper return-to-work assessment should therefore examine:

Medical condition

What condition exists?

Functional ability

What can the employee actually do?

Work requirements

What does the particular position require?

Restrictions

Are there limitations concerning:

• hours;
• workload;
• night work;
• travel;
• lifting;
• concentration;
• safety-sensitive duties?

Prognosis

Is the employee likely to sustain attendance?

6. Treating Physician vs Occupational Physician

This is a recurring issue in Japanese incapacity disputes.

The treating physician generally understands:

• the patient's clinical history;
• treatment;
• symptoms;
• recovery;
• medical prognosis.

The occupational physician can assess:

• workplace demands;
• occupational risks;
• work environment;
• fitness for the particular position;
• appropriate workplace restrictions.

Consequently, the two opinions can differ without either doctor necessarily being medically incompetent.

The MHLW specifically discusses situations where an employer seeks assessment by an occupational physician or designated specialist when the treating physician has certified fitness for work.

7. Six Important Japanese Case Laws

Case 1 — Obihiro Telephone & Telegraph Office Case

Supreme Court, First Petty Bench, March 13, 1986

This is one of the most important authorities concerning employer-directed medical examination.

The employee suffered from a work-related upper-limb/neck-shoulder condition. Under applicable collective and workplace health-management rules, the employer ordered a detailed medical examination by a physician designated by the employer.

The employee accepted examination by their own treating physician but refused the examination by the employer-designated doctor.

Disciplinary action followed.

The Supreme Court upheld the employer's authority to require the designated medical examination in the circumstances.

MHLW's own guidance cites this decision in its discussion of return-to-work medical assessments.

Principle

An employer can, under appropriate workplace rules and circumstances, require an employee to undergo a medical examination relevant to determining fitness for work.

However, this does not mean an employer can demand unlimited medical information.

The examination must have a legitimate employment-related purpose.

Case 2 — Tokyo Electric Power Company Case

Tokyo District Court, September 22, 1998

This case concerned a temporary employee with a serious disability who was repeatedly unable to attend work because of poor health.

The employer ultimately treated the employee as unable to perform the work.

The court accepted the dismissal as not constituting an abuse of dismissal rights because the employee's inability to attend work continued and the employee was considered physically and mentally unfit for the position. MHLW identifies this case as an example of dismissal based on inability to provide labour.

Medical evidence significance

The case demonstrates that evidence of incapacity should ideally establish:

• persistent inability to attend;
• functional inability;
• relationship between the condition and job duties;
• continuation of the incapacity;
• absence of a realistic short-term recovery.

A diagnosis by itself is less important than demonstrating actual inability to provide the contracted labour.

Case 3 — K Company Case

Tokyo District Court, February 18, 2005

The employee had frequent absences associated with manic depression and was unable to adequately perform duties even when attending work.

The employee was placed on leave.

After returning, frequent absences and recurrence continued and began affecting employment.

MHLW identifies this case as an example in its employment guidance concerning sickness-related inability to provide labour.

Principle

For incapacity dismissal, the employer should examine the whole employment history, rather than relying on a single medical certificate.

Relevant evidence can include:

• frequency of absence;
• repeated recurrence;
• performance during periods of attendance;
• attempted leave;
• return-to-work attempts;
• medical prognosis;
• whether the condition prevents sustained performance.

Case 4 — Dentsu Corporation Case

Supreme Court, March 24, 2000

The Dentsu case is principally a health-and-safety case, but it is highly relevant to medical evidence.

The employee had worked excessive hours and experienced serious psychological deterioration.

The Supreme Court recognized the employer's duty to prevent employees from suffering harm to their physical or mental health due to excessive accumulation of fatigue and psychological burden.

Medical evidence significance

Where an incapacity case concerns mental illness, evidence should not be confined to:

“Employee has depression.”

The relevant evidentiary picture may include:

• overtime;
• workload;
• workplace circumstances;
• symptoms;
• medical consultation;
• deterioration;
• leave;
• treatment;
• employer knowledge;
• causal relationship.

The Dentsu decision therefore illustrates the importance of connecting medical condition with workplace circumstances and functional consequences.

Case 5 — Supreme Court, June 8, 2015

2013 (Ju) No. 2430

This case concerned an employee who had suffered an employment-related disease and received medical compensation and temporary absence-from-work benefits.

The employee remained unable to return to work for an extended period.

The Supreme Court considered the interaction between:

• the Labour Standards Act;
• Industrial Accident Compensation Insurance Act;
• medical treatment;
• prolonged incapacity;
• dismissal restrictions.

The Court ultimately held that a worker receiving medical compensation benefits under the Industrial Accident Compensation Insurance Act could fall within the statutory framework allowing application of the discontinuance-compensation exception after three years.

Importance

This case demonstrates that medical evidence can have consequences beyond ordinary fitness-for-work disputes.

It can establish:

• existence of an employment-related illness;
• commencement of treatment;
• continuing incapacity;
• statutory workers' compensation status;
• duration of incapacity.

It therefore becomes particularly important where dismissal intersects with Article 19 of the Labour Standards Act.

Case 6 — Supreme Court, March 7, 2025

Police Inspector Case

2023 (Ju) No. 927

This recent Supreme Court decision concerned extremely heavy work, including long duty periods and repeated consecutive work.

The Court considered the employer's duty concerning accumulated fatigue and psychological burden. The case involved substantial overtime, repeated long duty periods and consecutive days of work.

Medical evidence significance

The case demonstrates why incapacity cases should be assessed using more than a medical certificate.

Evidence may include:

• working-hour records;
• duty rosters;
• overtime;
• consecutive shifts;
• medical records;
• symptoms;
• workplace complaints;
• supervisor knowledge;
• changes in employee behaviour;
• medical consultations.

The Supreme Court's approach illustrates the importance of evaluating the total factual and medical circumstances, rather than isolating one document.

8. What Should a Medical Certificate Contain?

For ordinary employment purposes, a useful certificate should preferably address functional capacity, not unnecessarily disclose sensitive medical details.

A useful structure is:

Employee

Name and employee identification.

Medical condition

Diagnosis or sufficiently clear medical description, where disclosure is necessary.

Work capacity

Whether the employee:

• cannot work;
• can work normally;
• can work with restrictions;
• can work reduced hours;
• can work progressively.

Expected duration

Estimated period of incapacity or date for reassessment.

Restrictions

For example:

• no night shifts;
• no overtime;
• reduced hours;
• no heavy lifting;
• limited travel;
• reduced workload.

Review date

When medical fitness should be reassessed.

9. What the Employer Should NOT Automatically Demand

A medical certificate should not automatically become a request for:

• complete medical history;
• unrelated illnesses;
• family medical history;
• every medication taken;
• unrelated specialist reports;
• private medical information having no connection with work capacity.

The employer should apply a necessity and proportionality approach.

The question should be:

“What medical information is reasonably necessary to determine whether the employee can safely and effectively perform the job?”

rather than:

“Give us your entire medical record.”

10. Employer's Independent Medical Examination

An employer may have legitimate grounds to request an independent or occupational medical assessment where:

1. the employee's certificate is ambiguous;
2. the employee's condition conflicts with observed work limitations;
3. the employee occupies a safety-sensitive position;
4. the employee seeks return from extended medical leave;
5. there is a substantial disagreement between medical opinions;
6. work restrictions need to be determined.

The Obihiro Telephone & Telegraph Office case is particularly important because the Supreme Court accepted the employer's authority to require an employer-designated medical examination in the circumstances of that case.

11. When Medical Opinions Conflict

Suppose:

Treating doctor:

“Employee is fit to return.”

Occupational physician:

“Employee is not currently capable of performing the original duties.”

The employer should not automatically accept either opinion.

It should investigate:

1. What question did each doctor answer?

“Medically recovered” does not necessarily mean:

“Able to perform this particular job.”

2. What evidence supports each conclusion?

3. What are the actual job demands?

4. Can restrictions resolve the problem?

5. Is reassignment feasible?

6. Is another medical assessment necessary?

7. What does the employee's work history show?

12. Incapacity vs Disability

The existence of a disability does not automatically establish inability to work.

The employer should distinguish:

Medical condition

↓

Functional limitation

↓

Impact on essential job duties

↓

Possibility of accommodation/reassignment

↓

Ability to continue employment

This is particularly important because an employer should not simply equate:

disability = incapacity = dismissal.

The evidence must establish the employment consequences.

13. Long-Term Illness and Dismissal

Where an employee has been absent for a prolonged period, the employer should normally examine:

1. medical prognosis;
2. expected recovery;
3. remaining leave period;
4. company sick-leave system;
5. possibility of return;
6. alternative duties;
7. rehabilitation;
8. reasonable workplace adjustments;
9. operational impact;
10. whether continued employment is realistically possible.

MHLW guidance specifically notes that dismissal may be considered where the employee has lost the ability to provide labour, while also identifying cases where dismissal was regarded as an abuse because recovery was expected or dismissal-avoidance measures such as leave were not offered.

14. Occupational Injury — Special Protection

Medical evidence becomes particularly important where the incapacity resulted from an occupational accident or occupational disease.

Article 19 of the Labour Standards Act generally restricts dismissal during:

absence from work for medical treatment for a work-related injury or illness

and for 30 days thereafter, subject to statutory exceptions.

The Supreme Court's 2015 case (2013 (Ju) No. 2430) is particularly important because it clarified the relationship between Industrial Accident Compensation Insurance benefits and the three-year dismissal restriction framework.

Thus, HR should establish:

• whether the illness is work-related;
• whether workers' compensation has been recognized;
• commencement of medical treatment;
• period of absence;
• continuing medical status;
• whether the statutory exception applies.

15. Burden of Proof

In litigation, the employer generally needs to substantiate the factual basis for dismissal.

The employee may provide:

• medical certificates;
• specialist reports;
• treatment records;
• evidence of ability to work;
• occupational physician reports.

The employer may provide:

• attendance records;
• job descriptions;
• medical examination results;
• occupational physician opinions;
• work-performance records;
• records of accommodations;
• leave records;
• return-to-work assessments;
• communications concerning medical restrictions.

The court will evaluate the evidence as a whole.

16. Practical Evidence Matrix

17. Recommended HR Procedure

A legally defensible Japanese incapacity process should normally follow this sequence:

Step 1 — Obtain appropriate medical documentation

Ask for a certificate addressing:

• work capacity;
• restrictions;
• expected duration.

Step 2 — Compare medical evidence with job requirements

Do not simply ask:

“Is the employee sick?”

Ask:

“Can the employee perform the essential functions of this position?”

Step 3 — Consult occupational physician

Particularly where:

• the employee works in a safety-sensitive role;
• the medical certificate is unclear;
• opinions conflict;
• return to work follows long-term leave.

Step 4 — Consider workplace measures

Consider:

• reduced hours;
• modified duties;
• reassignment;
• rehabilitation;
• phased return;
• temporary restrictions.

Step 5 — Review work rules

Check the company's:

• sick-leave rules;
• leave-of-absence provisions;
• medical examination rules;
• return-to-work rules;
• retirement/dismissal provisions.

Step 6 — Document the decision

Record:

• medical evidence considered;
• job requirements;
• restrictions;
• alternatives considered;
• reasons alternatives were rejected;
• employee communications;
• occupational physician opinion.

Step 7 — Consider dismissal only after the above

Where dismissal is contemplated, the employer should be able to demonstrate an objectively reasonable basis under Article 16.

18. Key Legal Principles

The Japanese position can be summarized as follows:

1. A diagnosis alone does not necessarily prove incapacity.
2. Functional ability is crucial.
3. The relevant question is often whether the employee can perform the particular job.
4. Treating-physician evidence is important but is not necessarily conclusive.
5. An occupational physician can provide workplace-specific evidence.
6. An employer may, under appropriate rules and circumstances, require a medical examination.
7. Long-term incapacity must be assessed together with prognosis and leave arrangements.
8. Employers should consider alternatives to dismissal where realistically available.
9. Work-related illness receives additional statutory protection.
10. Medical evidence should be proportionate to the employment decision.
11. Medical confidentiality should be respected.
12. Courts assess the totality of medical and employment evidence.

19. Conclusion

In Japan, medical evidence in incapacity cases is not simply a matter of obtaining a doctor's certificate and automatically accepting or rejecting it.

The critical legal question is generally:

What does the medical evidence establish about the employee's actual and foreseeable ability to perform the contractual work?

The strongest evidence therefore connects diagnosis → functional limitations → job requirements → prognosis → possible workplace measures.

The Obihiro Telephone & Telegraph Office case demonstrates that an employer can, in appropriate circumstances, require an employee to undergo an employer-designated medical examination.

The Tokyo Electric Power case and K Company case illustrate the relevance of persistent inability to attend or perform work in incapacity-dismissal disputes.

The Dentsu case shows the broader importance of medical and workplace evidence concerning mental and physical health. The 2015 Supreme Court case demonstrates the special importance of medical evidence where work-related illness and statutory dismissal restrictions are involved.

Finally, Japanese employers should remember that Article 16 of the Labour Contract Act requires an objectively reasonable basis and social acceptability for dismissal. Consequently, a medically documented condition should not automatically be treated as grounds for dismissal without considering prognosis, leave, work capacity, possible adjustments and other relevant circumstances.

Six principal cases/authorities

1. Obihiro Telephone & Telegraph Office Case, Supreme Court, 13 March 1986.
2. Tokyo Electric Power Company Case, Tokyo District Court, 22 September 1998.
3. Dentsu Corporation Case, Supreme Court, 24 March 2000.
4. K Company Case, Tokyo District Court, 18 February 2005.
5. 2013 (Ju) No. 2430, Supreme Court, 8 June 2015.
6. Police Inspector Case, Supreme Court, 7 March 2025, 2023 (Ju) No. 927.

The case law above is focused on Japanese employment incapacity, medical examination, occupational health, sickness absence and dismissal principles. Not every case establishes a specific “medical evidence requirement”; some establish the surrounding legal principles that determine how medical evidence is evaluated.