Indexation managed by a real estate agency

Brief answer

In Belgium, a real estate agency mandated by the landlord can legally notify indexation to tenants (article 1984 of the old Civil Code on mandate). The service is generally included in full rental management (5-8% of the monthly rent). In case of omission or error by the agency, its contractual liability is engaged and allows the landlord to recover the prejudice not covered by the 3 months of legal retroactivity of the request (art. 1728bis, §1 of the Civil Code).

The rental management mandate: legal framework

The agency acts on behalf of the landlord by virtue of a written mandate (article 1984 of the old Civil Code). Three elements structure this mandate:

1. The nature of the mandate

The rental management mandate is generally general (covers all current administration acts) and remunerated (commission or fees defined in the contract).

For indexation specifically, the mandate must explicitly mention the power to notify annual indexations. This is the case by default in all standard contracts of the professional federations (Federia, CIB, BIV).

2. Agency obligations

The agency is bound by an obligation of means on administrative management and an obligation of result on the collection and remittance of rents. Concretely:

• Track anniversary dates of managed leases
• Calculate indexations according to the official formula
• Notify tenants by registered mail in useful time
• Remit to the landlord the indexed rent after commission
• Keep monthly accounting accessible to the landlord

Any failure on these points may engage the contractual liability of the agency.

3. Landlord obligations

The landlord remains owner of the right to index — the agency is only a mandatary. The landlord must:

• Provide lease documents (copy, registration proof)
• Accept the indexation project or give carte blanche according to the mandate
• Pay the commission (generally deducted at source from the rents collected)

Typical rental management costs

Service	Usual pricing	For rent 1,000 €/month
Full rental management	5-8% of monthly rent collected	600-960 €/year
Indexation only (flat fee)	50-150 € per lease/year	50-150 €/year
Formal notice / collection	80-150 € per file	On use
Justice of the peace procedure	200-500 € (excluding lawyer)	On use
Entry/exit inventory	200-400 €	One-time
Search for new tenant	50-100% of 1st month	Once per rotation

For an investor with a single property, in-house management remains far more profitable: a few hours a year to save ~700 €. From 3-5 properties, delegation becomes economically justified by the time gain.

How indexation by the agency works concretely

Step 1: Tracking anniversary dates

The agency maintains a database of managed leases with anniversary dates. An automatic alert system signals each date 60-90 days in advance.

Step 2: Monthly calculation at Statbel publication

Around the 26th of each month, the agency collects the new Statbel health index and launches automatic calculation for all leases whose anniversary falls within the following 60 days.

Step 3: Validation by the landlord (per mandate)

According to the management contract:

• Broad mandate: the agency notifies without prior validation
• Mandate with validation: the agency transmits the project to the landlord, who approves by email (response within 48h on average)

Step 4: Notification to the tenant

The agency sends the registered mail with AR or the eBox electronic registered mail to the tenant, in its own name but clearly mentioning the mandate (« Agency X, mandatary of Mr/Mrs Y »).

Step 5: Payment follow-up

The agency verifies the adjustment of the tenant’s standing order at the next due date. In case of non-payment, automatic formal notice within 15 days, then escalation according to the mandate.

If the agency forgets or makes an error

This is a real risk. Several scenarios:

Scenario 1: Simple omission

The agency has not indexed for 1-3 years for a lease. Consequence:

• Landlord can recover the last 3 months from the tenant (retroactive effect of the request, art. 1728bis, §1)
• For the period lost beyond: liability action against the agency (professional fault)
• Prejudice calculation: cumulative difference between the theoretical rent and the rent effectively collected over the unrecoverable period

Scenario 2: Erroneous calculation

The agency applied an incorrect formula (wrong index, omission of the regional EPC coefficient, etc.). Consequence:

• Indexation contestable by the tenant
• The landlord can renotify correctly (effect for future months only)
• The agency generally compensates the difference for past months

Scenario 3: Notification not received by the tenant

The agency sent by simple letter without proof of receipt, or to an outdated address. Consequence:

• If the tenant contests having received, the agency bears the burden of proof
• Recommendation: renotify by registered mail and accept the loss of past months

Procedure for recourse against the agency

1. Written formal notice detailing the fault (omission, calculation error, default of notification) and the quantified prejudice
2. 15-30 day deadline for response
3. If refusal, conciliation before the IPI (executive professional chamber)
4. As a last resort, justice of the peace (litigation up to 5,000 €) or court of first instance (beyond)

Many agencies offer an amicable compensation as soon as formal notice is given, to preserve their reputation and avoid a public IPI decision.

Criteria to choose an agency well

For a landlord hesitating to delegate, here are the 5 questions to ask any candidate agency:

1. Do you have an automatic alert system for lease anniversary dates?
2. What is the procedure in case of payment delay or refusal of indexation by the tenant?
3. How much is your commission on management (% of rent collected or flat fee)?
4. What is your insurance coverage for professional faults?
5. Can you provide me with a detailed monthly reporting of the acts performed?

The absence of a clear answer to one of these questions is a warning sign. A serious agent has precise and quantified answers on all these points.

When to take over yourself?

Three classic situations:

Situation A: Reduction of the property portfolio

The landlord goes from 5 to 1 property (gradual sale). The agency commission becomes disproportionate to the time saved. Take back management and use a calculator for annual indexations + a notification template suffice.

Situation B: Repeated dissatisfaction

Calculation errors, notification omissions, lack of communication. Better to terminate the mandate (1-3 month notice generally) and either change agency or take back in direct.

Situation C: Low rent (< 600 €/month)

For a rent of 500 €/month, 7% commission = 35 €/month = 420 €/year. Disproportionate for a simple annual indexation that takes 30 minutes per year in direct management.

Practical consequence: indexation is a simple act

The central argument for direct management is that indexation takes ~30 minutes per year per property:

• 5 minutes: verification of the anniversary date and publication of the Statbel index
• 5 minutes: calculation via the calculator
• 10 minutes: editing the letter from the template
• 10 minutes: sending by registered mail (paper or eBox)

To compare with 600-960 €/year of agency commission for full management. For 1-2 properties, direct management is trivial and infinitely more profitable.

For 5+ properties, delegation becomes a real comfort — especially for landlords not mastering the legal matter or living far from the property.

To go further

• Landlord rights — including the right to mandate
• I forgot to index — recourse against agency included
• How to notify the tenant — mandatory elements
• Notification template — form letter
• Registered mail mandatory? — accepted formats
• Calculate my indexation — official tool
• When to notify the tenant? — optimal calendar
• Methodology — legal sources

Delegating rental management to an agency remains an organisational choice, not an obligation. Indexation itself is a simple technical act, accessible to any landlord who takes 30 minutes per year per property.