Belgium’s sick leave law requires employers to pay guaranteed salary (gewaarborgd loon) for the first 30 calendar days of illness, after which the employee’s mutual insurance fund (mutualité/ziekenfonds) takes over with sickness benefits. The system is governed by the Law on Guaranteed Wages (Loi sur les salaires garantis) and supervised by the National Social Security Office (ONSS/RSZ).
Key Takeaways
- Employers must pay 100% of gross salary for the first 30 calendar days under the Guaranteed Wages Law
- After day 30, the mutual insurance fund pays sickness benefits at approximately 60% of capped gross salary
- A medical certificate is required within 2 working days of the first day of absence
- Employers can reclaim a portion of guaranteed salary costs through the Fedasil system
- The employer must notify the ONSS and maintain detailed sick leave records
Belgium’s Sick Leave Entitlement
Belgium’s sick leave system operates on a clear two-stage structure. Under the Law on Guaranteed Wages (Loi du 12 avril 1965), the employer pays the employee’s full salary for the first 30 calendar days of illness. After this period, the mutual insurance fund (mutualité or ziekenfonds) provides sickness benefits.
The guaranteed salary period is a strict maximum of 30 calendar days. It cannot be extended by the employer and does not restart for a new illness within 30 days — if the employee returns and falls ill again within that window, the remaining days of the original 30-day period apply.
For employees in specific sectors or under certain collective agreements, the guaranteed salary period may be shorter (e.g., 14 days in some cases) or longer.
Who Pays for Sick Leave?
| Period | Pay Rate | Who Pays |
|---|---|---|
| Days 1–30 | 100% of gross salary (capped) | Employer |
| Days 31+ | ~60% of capped gross salary | Mutual insurance fund |
The employer cannot shift the guaranteed salary obligation to the employee or to social security. The first 30 days are always the employer’s responsibility.
Sick Leave Pay Rates
| Period | Pay Rate | Maximum Base (2026 approx.) | Source |
|---|---|---|---|
| Guaranteed salary (days 1–30) | 100% of gross salary | Capped at €11,105.26/month (2025 figure) | Law on Guaranteed Wages |
| Mutual fund benefit (days 31+) | ~60% of capped gross salary | Indexed annual ceiling | Social Security Code |
| Exceeding ceiling | No additional payment | — | — |
The guaranteed salary cap is linked to the maximum social security contribution base. For 2025, the monthly ceiling was approximately €11,105.26 gross. This cap also applies to the mutual fund benefit calculation.
Medical Certificate Requirements
Belgium has strict medical documentation requirements:
- Days 1–3: Employee may self-certify (attestation de force majeure) for brief absences, but the employer may require a certificate from day 1 if stated in the employment regulations
- From day 4: A medical certificate (certificat médical) from a doctor is mandatory
- Within 2 working days: The certificate must be provided to the employer
The certificate must specify the expected duration of absence. For absences exceeding one month, the employer may request periodic updates.
Employers who fail to obtain the certificate within the prescribed timeframe may lose the right to reclaim guaranteed salary costs.
How to Calculate Sick Pay in Belgium
Example: An employee earning €4,500/month gross is off sick for 40 calendar days.
- Guaranteed salary (days 1–30): €4,500
- Mutual fund benefit (days 31–40): 10 days
- Daily mutual fund benefit: (€4,500 × 0.60) ÷ 30 = €90/day
- Mutual fund payment: €90 × 10 = €900
Total paid to employee: €4,500 (employer) + €900 (mutual fund) = €5,400
The employer can potentially reclaim a portion of the guaranteed salary through the ONSS reimbursement mechanism.
Guaranteed Salary Reimbursement
Employers can reclaim guaranteed salary costs through the social security system:
- The employer files the claim through the ONSS/RSZ declaration
- Reimbursement is made through the Fedasil (Federal Agency for Payments of Sick Leave) system
- The amount is subject to the employer’s social security contribution history
- Claims must be filed within the prescribed timeframe through the social security portal
The reimbursement does not cover 100% of the guaranteed salary — the employer typically bears a portion as a cost-sharing mechanism.
Employer Obligations and Penalties
Belgian employers must:
- Pay guaranteed salary for the first 30 calendar days
- Obtain and maintain the medical certificate within 2 working days
- Report the absence to the ONSS through the Dimona system
- Maintain sick leave records for at least 5 years
- Cooperate with the employer’s prevention advisor for occupational health matters
Non-compliance can result in fines from the Social Inspection Office (Sociale Inspectie), loss of reimbursement rights, and potential employment court proceedings.
Comparison With Other Countries
| Country | Sick Days | Pay | Certificate Required |
|---|---|---|---|
| Belgium | 30 days guaranteed + mutual fund | 100% employer / 60% mutual fund | Day 4 (or day 1 if agreed) |
| UK | 28 weeks SSP | £116.75/week | Day 7 |
| Australia | 10 days personal/carer’s leave | Full rate | 2+ consecutive days |
| US | Varies by state | Varies | Employer policy |
FAQ
Can the guaranteed salary period be shorter than 30 days?
In some sectors and under certain collective agreements, the guaranteed salary period may be shorter — for example, 14 days in some manual worker agreements. However, the statutory minimum under the Law on Guaranteed Wages is 30 calendar days. Employers cannot reduce this below the statutory floor.
What happens if the employee’s salary exceeds the guaranteed salary cap?
If the employee’s actual salary exceeds the capped amount (approximately €11,105.26/month), the employer must still pay 100% of the full salary for the first 30 days. However, the mutual fund benefit after day 31 is calculated only on the capped amount. The gap between the employee’s actual salary and the capped amount is not covered by the mutual fund.
Can the employer reclaim guaranteed salary costs?
Yes, through the ONSS/RSZ system and the Fedasil reimbursement mechanism. The employer must file the claim within the prescribed timeframe. The reimbursement covers a portion of the guaranteed salary paid, subject to the employer’s social security contribution history and the applicable rules.
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