Can indexation cause rent to decrease?

Indexation can theoretically lower the rent

The formula works both ways:

• If new index > starting index: rent increases (normal case)
• If new index = starting index: rent stays the same
• If new index < starting index: rent decreases (very rare)

In practice, the Belgian health index has shown a consistent upward trend over decades. A decrease would require a sustained period of deflation.

When could this happen

A rent decrease through indexation would require the health index to drop below the level it was at when the lease was signed. Scenarios where this could theoretically occur:

• Sustained deflation: a prolonged period of falling prices across the economy
• Economic crisis: a severe recession causing widespread price decreases
• Recently signed leases: a lease signed just before a deflationary period would have a high starting index

In all cases, the tenant could request the landlord to apply the lower indexed rent, using the same formula and written request procedure.

Historical perspective

The Belgian health index has shown a consistent upward trend:

Brief periods of stagnation or very slight decreases have occurred (notably in 2015), but never enough to significantly reduce indexed rents for most leases.

Regional specifics

Brussels-Capital Region

Under the Ordinance of 27 July 2017, the formula applies identically whether the result is an increase or decrease. EPC restrictions do not apply to downward indexation.

Wallonia

The Decree of 15 March 2018 does not distinguish between upward and downward indexation. The same formula applies.

Flanders

The Flemish Housing Rental Decree of 9 November 2018 applies the same formula regardless of direction. EPC restrictions are irrelevant for downward adjustments.