Landlord rights regarding rent indexation
Complete inventory of the Belgian landlord's rights regarding indexation: index, waive, claim, contest. Legal sources and limits.
Brief answer
The owner of a rented property in Belgium has several cumulative rights regarding indexation: right to index once a year on the anniversary date, right to notify without prior notice, right to waive for a year, right to claim retroactively (up to 3 months), right to seize the justice of the peace, right to mandate a third party. The only strict safeguard: a single adjustment per year (article 1728bis of the Civil Code).
Overview: the Belgian landlord controls the timing, rhythm, and magnitude of their indexation — within the limit of once a year and the official formula. It is a unilateral right that requires neither agreement nor addendum.
Inventory of landlord rights
| Right | Legal source | Limit |
|---|---|---|
| Index once a year | Art. 1728bis §1 CC | A single indexation per rental year |
| Notify without prior notice | No legal notice required | Effect from receipt |
| Waive indexation for a year | Contractual freedom | No legal precedent |
| Claim retroactively | Art. 1728bis §1 CC | 3-month cap |
| Refuse an instalment plan | Contractual freedom | None (but can harm the relationship) |
| Seize the justice of the peace | Art. 591 Judicial Code | Free procedure ~50 € fiscal stamp |
| Mandate a third party | Art. 1984 CC (mandate) | Written mandate recommended |
| Keep the benefit if contestation rejected | Constant case law | None |
| Combine with triennial revision | 1991 law, art. 7 | Exceptional revision (>20% value) |
None of these rights require the prior agreement of the tenant. All are exercised by simple written notification.
Detail of the main rights
1. The right to index (core of the system)
This is the fundamental right. On each anniversary date of the lease’s entry into force, the landlord can send a written indexation request to the tenant, calculated according to the official formula of article 1728bis.
Conditions to respect:
- Lease registered at the registration office (otherwise: no right, see our unregistered lease guide)
- Written request (simple letter, registered or explicit email — no oral mention)
- Calculation compliant with the formula (
Rent × New index ÷ Base index × EPC coef.) - EPC coefficient correctly applied according to region and signature date
See how to calculate an indexation for the step-by-step method.
2. The right to notify without prior notice
Article 1728bis imposes no prior deadline between notification and the anniversary date. The landlord can send the registered mail:
- Several months in advance (limited by the availability of the health index of the month preceding the anniversary)
- 1 month before (optimal timing, cf. our when to notify guide)
- The day of the anniversary itself
- Several months after the anniversary (with loss of monthly payments between anniversary and receipt, but the right remains intact)
The myth of « mandatory prior notice » circulates widely but is false in Belgian law. See our debunking in when to notify the tenant.
3. The right to waive for a year
The landlord can freely waive indexation for a given year, with no legal consequence:
- No addendum to sign
- No special notification to the tenant
- No precedent that would prevent indexing the following years
Typical cases of waiver:
- Commercial gesture towards a good tenant (loyalty)
- Tenant in financial difficulty (temporary respite)
- Very low inflation where the gain would be negligible (e.g. < 5 €/month)
- Lease soon ending where the administrative effort isn’t worth it
The waiver is tacit by default: without a written notification, no indexation is due. And in case of late notification, the landlord only recovers for the past the 3 months preceding the month of the request (article 1728bis, §1 CC) — earlier monthly payments are definitively lost.
4. The right to claim retroactively
If the landlord has forgotten to index for several years, they can recover the last 3 months preceding the month of their request by notifying late (article 1728bis, §1 CC). Beyond that, it is definitively lost. For the future, however, the request applies in full: the fully indexed rent is due from notification.
Detailed procedure in our guides:
5. The right to seize the justice of the peace
If the tenant contests the indexation without valid ground, the landlord can seize the justice of the peace of the commune of the dwelling:
- Free procedure (fiscal stamp ~50 €)
- Without mandatory lawyer
- Hearing delay 4 to 8 weeks
- The landlord obtains an executory title (judgment) if successful
- Possibility to mandate a bailiff for forced execution (seizure on account or salary)
See our legal contestation guide for the complete procedure.
6. The right to mandate a third party
The landlord can delegate the exercise of their right to a representative (agency, syndic, notary, real estate expert, accountant). The written mandate must be attached to the notification or available on the tenant’s request. This delegation is very frequent in investment portfolios of more than 5 properties, where administrative management becomes time-consuming.
The mandate generally costs 5 to 8% of the monthly rent at an agency in full rental management, or 30-80 € annual flat fee at a specialised accountant.
Limits and safeguards
All these rights are not without counter-powers. The landlord must deal with:
| Limit | Effect |
|---|---|
| A single indexation per year | No fractionation, no recovery beyond the 3 months |
| Mandatory registered lease | Without registration, no right |
| Calculation compliant with formula | Erroneous calculation = valid tenant contestation |
| Regional EPC coefficient | In Bxl pre-2022 and Flanders, EPC caps |
| Retroactivity limited to 3 months | Beyond, arrears definitively lost |
| Effect at receipt | Not retroactive beyond the date of receipt |
| No free rent modification | The rent remains contractually stable |
The landlord’s right is exercised within a strict formal framework. Stepping outside the framework = losing the right (most frequent case: forgetting to send a written notification and wrongly believing that indexation is « automatic »).
Typical practical cases
Case 1: The landlord wants to index but the tenant turns a deaf ear
Action: send a registered mail with acknowledgement of receipt including the detailed calculation. If no payment at the next due date, send a formal notice (15 days to regularise). Without response, seize the justice of the peace.
Case 2: The landlord has forgotten for 4 years
Action: send the notification immediately (with calculation of the complete chain over 4 years). Claim only the last 3 months of arrears (the rest is lost). For the future, the new rent applies fully.
Case 3: The landlord wants to waive this year
Action: nothing to do. The waiver is tacit. The landlord can index normally at the next anniversary date, on the basis of the current unindexed rent.
Case 4: The landlord buys a property already rented
Action: recover the lease documents from the seller, verify the registration, notify the change of owner to the tenant (with IBAN), then exercise the right to index at the next anniversary date or recover up to 3 months if the previous owner had forgotten. See our owner change guide.
Case 5: The landlord wants their agency to index
Action: sign a written rental management mandate explicitly including the indexation mandate. The agency will send registered mails in its own name, mentioning the mandate. The landlord receives an annual invoice for this service.
Landlord rights vs tenant rights
For the inverse perspective (the rights the tenant has facing an indexation), see our tenant rights guide.
Comparative summary:
| Subject | Landlord right | Tenant right |
|---|---|---|
| Index the rent | Yes, 1×/year, no agreement | No |
| Refuse the indexation | — | Only if valid ground |
| Waive indexation | Yes, freely | — |
| Request an instalment plan | — | May request, landlord may refuse |
| Seize the justice of the peace | Yes, against recalcitrant tenant | Yes, against invalid indexation |
| Mandate a third party | Yes (agency, syndic) | Yes (defence lawyer) |
The Belgian system is asymmetrical for the landlord’s benefit: they hold the lever, the tenant can only verify the formal compliance of the request.
To go further
- When can one index a rent? — calendar and rules
- How to calculate an indexation — step-by-step method
- When to notify the tenant? — optimal timing
- Tenant rights — inverse perspective
- Retroactive indexation — exercising the right after omission
- Calculate my indexation — official tool
- Notification template — form letter
- The law on indexation — detailed sources
- Tenant refusal: remedies — procedure if disagreement
The Belgian landlord has a much wider range of rights than is generally believed. The real question is not « do I have the right? » but « how to exercise this right with method and tact ».
Frequently asked questions
When exactly can the landlord index the rent in Belgium? + −
On each anniversary date of the entry into force of the lease, at most once per year (article 1728bis of the Civil Code). The lease must be registered and the request must be made in writing. No legal prior notice is required before the anniversary date — the notification can occur before, on the day itself or after. It is a right, not an obligation: the landlord can waive a given year without losing their right for following years.
Can the landlord refuse a payment plan? + −
Yes. The landlord has no legal obligation to accept an instalment plan for indexation arrears. The tenant must in principle pay the indexed rent from the first due date following notification. In practice, accepting an amicable instalment plan preserves the relationship and avoids the justice of the peace — it is a commercial choice, not a legal concession.
Can the landlord index multiple times per year? + −
No. Article 1728bis limits indexation to once per rental year, on the anniversary date. An indexation 'in the middle of the year' or 'every 6 months' is null and not enforceable against the tenant. The only possible modulation is to waive indexation for a year (definitive loss of that indexation) or to notify late (with loss of monthly payments until receipt).
Can the landlord modify the rent outside indexation during the lease? + −
Very rarely. The rent set in the lease is in principle stable for the entire duration. Three exceptions: annual indexation (automatic mechanism), addendum signed by mutual agreement with the tenant, or exceptional triennial revision (at 3, 6 or 9 years, mandatory justice of the peace, justification of >20% variation in rental value). In practice, indexation is the only regular tool available to the landlord.
Can the landlord transmit their right to index to a representative? + −
Yes. The landlord can mandate a third party (agency, syndic, notary, accountant) to exercise their right to index in their name. The mandate must be written and attached to the notification. The tenant is required to accept the representative's notification on the same basis as the landlord's. This delegation is very frequent in real estate investment portfolios of more than 5 properties.
If the tenant contests the indexation, does the landlord lose their right? + −
No. The contestation simply suspends the enforceability of the indexation, but does not call into question the landlord's right. If the contestation ground is invalid (most frequent case), the landlord seizes the justice of the peace and prevails. The indexation request has already been notified and its effects are acquired at that date — the landlord therefore loses nothing by letting the dispute resolve itself.
Calculate your indexation
Our tool automatically applies the Belgian legal formula with up-to-date Statbel indexes.
Go to the calculator →This article is informational and does not constitute legal advice. For any disputed or complex situation, consult a lawyer or the justice of the peace of the property's commune (free procedure).