Indexation is not a rent increase: it maintains value. Here is what it means concretely for your return.
Indexation does not make the property more expensive in real terms: it simply compensates for the loss of purchasing power of money. A rent of 800 euro in 2015 corresponded to a certain basket of goods and services; in 2026 you need roughly 950 euro to buy that same basket. The tenant therefore pays no more in real terms, and the landlord earns no more: the balance stays exactly as originally agreed.
Skipping indexation for one year does not only cost you that year's increase. Because the calculation always starts from the base rent and the initial index, a later catch-up is limited to three months. The shortfall therefore repeats every following year. On a rent of 800 euro with average inflation, a single missed year can amount to several hundred euro annually and several thousand over the life of the lease.
A Flemish lease starting at 700 euro in 2015 and correctly indexed each year reaches around 953 euro in 2026. Cumulatively that represents almost 15,000 euro of additional rental income over ten years, purely because indexation was applied on time each year. A landlord who missed half of those indexations now receives a noticeably lower rent, and that gap can no longer be recovered.
Property tax, insurance, maintenance, repairs, management fees: all of these follow inflation. If the rent stays frozen while costs keep rising, your net return falls every year. Indexation is the only lawful mechanism that keeps the contract in balance over time, without having to renegotiate the lease or look for a new tenant.
Indexation is not a rent increase: it maintains value.
Tenants' incomes also follow the index: salaries, pensions and benefits in Belgium are indexed using the same health index. An annual indexation is therefore a moderate and predictable increase, usually a few tens of euro. That is considerably easier to absorb than a sudden catch-up after several forgotten years, or a renegotiated rent when the property is re-let.
The law gives you the right to index, but does not do it for you. Without a written request to the tenant the rent stays unchanged. This is precisely where many landlords lose money: not by choice, but through forgetfulness, uncertainty about the anniversary date, or reluctance to raise the subject with their tenant.
Many landlords hesitate to claim indexation for fear of straining the relationship. An official, impersonal letter sent by a third party changes the nature of the conversation: it is no longer the landlord asking, but a legal calculation being applied, backed by official index figures. Most tenants accept it without discussion when the calculation is transparent.
For 30 euro per year per contract, the indexation is calculated and the letter drafted and sent to your tenant, with you in copy. On an average rent, the annual increase far exceeds that amount in the very first year. In other words: the service pays for itself several times over, and you no longer have to think about it.
Enter your base rent, start date and region and see straight away what you may charge this year. Based on the official health index, with the Flemish EPC correction applied automatically.
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