In Belgium

Rent revaluation is often confused with indexation, but the two are distinct:

  • Indexation: annual automatic adjustment per the health index. Does not modify the base rent.
  • Revaluation: increase of the base rent itself, to bring it closer to market value. Only at specific moments.

The only two moments when the landlord can revalue rent:

  1. Triennial review: between the 9th and 6th month before the triennial end, if rental value changed by 20%+
  2. Between leases: when a tenant leaves and a new one arrives, the landlord freely sets a new rent

Any increase outside these two frameworks is illegal.

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Warning
A landlord who sends a letter announcing a rent increase of 50 EUR “because prices have risen” is acting outside the legal framework. The tenant can refuse and is not obliged to pay the supplement.

Practical example

A landlord rents at 750 EUR/month for 5 years. The market has evolved to 950 EUR. They cannot simply raise to 950 EUR. Options: request a review at the end of the 2nd triennial (if +20% justified), or wait for the lease end to set 950 EUR for the next tenant.