Indexation after an owner change: who can index?
Sale, inheritance, donation: what becomes of the indexation right when a rented property changes owner? Rules, dates and lease continuity.
Brief answer
In Belgium, a change of owner of a rented property never interrupts the lease: the new buyer automatically takes over all rights and obligations, including the right to indexation (article 9 of the law of 20 February 1991). The base index remains that of the original signature, not of the sale. Retroactive recovery is capped at the 3 months preceding the month of the request (article 1728bis, §1 of the Civil Code), even when the indexation delay is due to the previous owner.
Immediate action after purchase: send the tenant a letter indicating the change of owner, the IBAN for rents, and the transfer date. Then, check the indexation chain to identify any possible recoveries within 3 months.
The principle: automatic lease continuity
Article 9 of the law of 20 February 1991 on rental leases lays down a clear rule: the registered lease is enforceable against the new buyer. Concretely, upon a sale:
- The lease continues on the same terms (duration, rent, clauses)
- The new buyer substitutes for the old owner (« legal assignment »)
- The tenant retains all their rights (right to remain in the premises, guarantee, notice formulas)
- The new landlord takes over all the rights of the previous one: collection of rents, annual indexation, requirement of the rental guarantee, etc.
If the lease is not registered, enforceability is more fragile (the buyer can terminate with a special notice), but indexation remains impossible due to non-registration (see our unregistered lease guide).
Original date: the initial signature, not the sale
This is the most frequent error. For indexation calculation, the date that counts is always the original signature of the lease between the previous owner and the tenant, not the date of the deed of purchase.
Practical consequence: the base index (month preceding signature) remains frozen for the entire duration of the lease, regardless of successive owner changes.
| Step | Date | Effect on indexation |
|---|---|---|
| Lease signature | 1 June 2018 | Base index = May 2018 |
| Sale of the property | 15 March 2024 | No change in base |
| 1st indexation by new owner | 1 June 2024 | Calculation: index May 2024 ÷ index May 2018 |
| Following indexation | 1 June 2025 | Calculation: index May 2025 ÷ index May 2018 |
Our calculator automatically applies this logic: enter the original signature date and the indexation date, without worrying about the purchase date.
Recovery of indexations « forgotten » by the previous owner
Typical case: you buy in 2025 a property rented since 2018. The previous owner has never indexed. Can you recover the 7 past years of indexations?
Answer: no, except for the last 3 months.
Article 1728bis, §1 of the Civil Code limits the retroactive effect of the request to the three months preceding the month of the request, and this cap applies to the lease (and therefore to the property), not to the owner. Concretely:
- If the previous owner notified nothing in 7 years: all arrears beyond 3 months are lost
- The new owner can recover the last 3 months preceding the month of their first notification to the tenant
- For the future, however, the request applies in full: the fully indexed rent is due from notification
- The recovery is calculated on the complete chain of theoretical indexations (cascade) — see our retroactive indexation guide for detail
The purchase of a rented property therefore does not erase the omission history of the previous owner, but allows the new one to immediately recover the still recoverable share.
Recommended procedure after buying a rented property
1. Recover the lease documents
Before signing the authentic deed, require from the seller:
- Complete copy of the lease (all pages, annexes)
- Proof of registration (extract of the registration file)
- History of indexations already applied (notified letters, indexed transfers)
- Tenant contact details (name, phone, email)
- Detail of the rental guarantee (blocked account, amount, bank)
2. Notify the tenant of the change
Within 15 days following the deed, send a letter to the tenant:
« Madam, Sir, I inform you that I have become the owner of the property you occupy located at [address], by deed of [date]. The lease continues on the same conditions. From [transfer date], please make the monthly rent payment to the following bank account: [IBAN]. For any question, you can reach me at [contact]. »
No mandatory official template — a simple letter suffices. Registered mail is not indispensable but advised for traceability.
3. Rebuild the indexation chain
Use the calculator to check:
- What should the theoretical rent be in 2026 (full chain since signature)?
- What rent does the tenant currently pay?
- Monthly difference and recoverable arrears (3 months maximum)
This analysis takes 5 minutes and often reveals an indexation delay at the previous owner’s level.
4. Notify the (new) indexation if relevant
If indexation delay detected, send an indexation notification by registered mail with acknowledgement of receipt, following the notification template. Specify the new monthly rent and the recovery of the 3 months.
For procedure detail, see our retroactive indexation guide.
Special case 1: inheritance
Upon the death of the landlord, the heirs automatically take over the lease (article 1742 of the old Civil Code). During the succession phase (before the partition):
- The succession indivision collects the rents and can index
- A majority of indivisaries suffices for ordinary administration acts (including indexation)
- Rents are paid to an indivision account, to be distributed among heirs according to the shares
After the partition or sale of the property, the attributing heir (or the buyer) takes over alone the continuation. Everything is legally continuous: no indexation lost, no special notification necessary to the tenant (except change of IBAN).
Special case 2: split ownership (usufruct / bare ownership)
Very frequent in family successions (donation with usufruct reservation). Rules:
- The usufructuary is sole holder of the right to rents — therefore sole entitled to index
- The bare owner has no right on the rent or on the indexation
- The usufructuary must notify the indexation to the tenant in their own name (the lease remains attached to the property, but the rent beneficiary is the usufructuary)
- If the usufruct is extinguished (death), the full owner immediately recovers all rights — they will have to notify the tenant for the IBAN change and resume the indexation chain at the next anniversary date
Special case 3: donation between living persons
The donation of a rented property follows the same rules as sale: the donee takes over the lease as is. The only difference is fiscal (donation duties instead of sale registration duties), without impact on indexation.
Special case 4: forced sale (seizure, bankruptcy)
In a public sale on seizure or liquidation, the buyer takes over the lease if it is registered. If the lease is not registered, the buyer can terminate with a special notice (generally 3 months). Indexation follows the usual rules from the transfer.
Frequent errors to avoid
| Error | Consequence |
|---|---|
| Calculate indexation on the index of the month of the deed of purchase | Invalid calculation, tenant contestation |
| Consider the sale as a new lease | False, the original lease continues |
| Refuse the tenant’s right to remain in the premises | Civil offence, possible conviction |
| Demand a new rental guarantee | Not legal, the initial guarantee subsists |
| Notify indexation without checking lease registration | Indexation contestable if lease not registered |
| Claim more than 3 months of arrears under the previous owner | Tenant can refuse the excess part |
| Forget to transmit the IBAN to the tenant | Confusion, payments to the old owner |
To go further
- When can one index a rent? — annual calendar after sale
- Retroactive indexation: rules — recovery limited to 3 months
- 9-year lease and indexation — continuity after change
- Tenant letter form — mandatory elements
- Unregistered lease — risk for the buyer
- Notification template — adaptable form letter
- Calculate the official indexation — applies the chain automatically
- Methodology — legal sources
Buying a rented property means buying an ongoing lease — and its entire indexation history. Purchase due diligence must include verification of this chain, on pain of recovering a rent frozen for years.
Frequently asked questions
When a rented property is sold, does the new owner inherit the indexation right? + −
Yes, automatically. The lease continues with the new buyer on the same terms (article 9 of the law of 20 February 1991). The new owner takes over all the rights and obligations of the previous landlord, including the right to indexation, from their own entry into the lease. No addendum is required: the sale of the property triggers automatic transfer of the lease.
On which original date is indexation calculated after sale? + −
On the original signature date of the lease, not the sale date of the property. The base index remains the one of the month preceding the initial signature between the old owner and the tenant. The sale of the property never resets the lease. This rule is crucial: a property bought in 2025 but rented since 2018 has a base index of 2018, not 2025.
Can the new owner catch up indexations forgotten by the previous one? + −
Only very partially. The indexation request only has retroactive effect for the 3 months preceding the month of the request (article 1728bis, §1 of the Civil Code). If the previous owner never indexed for 5 years, the new buyer can therefore only recover the last 3 months of arrears from their first written notification. For the future, however, the fully indexed rent (complete formula from the base rent) applies from the request.
In case of inheritance, do the heirs continue the indexation? + −
Yes. The heirs of a landlord take over all the rights and obligations of the deceased on the lease (article 1742 of the old Civil Code). They can therefore continue to index at the usual anniversary dates, including an indexation forgotten by the deceased within the limit of the 3 months preceding the month of the request. The transition is legally transparent.
Should the tenant be informed of the sale? + −
No formal legal obligation, but strongly recommended. A simple letter from the new owner informing of the change (with contact details, IBAN for rents, transfer date) avoids confusion. Without this information, the tenant can continue to pay the old owner in good faith — and the new one will then have to recover the rents from the previous owner.
Special case: split ownership (usufruct / bare ownership) + −
The usufructuary is sole holder of the right to collect rents, therefore sole entitled to index. The bare owner has no right on the rent or on the indexation. If the usufruct is transferred or extinguished (death of the usufructuary), the full owner recovers all rights, including the continuation of annual indexations. This situation is frequent in family successions (donation with usufruct reservation).
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).