Rent indexation in Flanders, October 2025
Your lease has its anniversary in October 2025? Here is the health index to use, the formula, and what Flanders adds on top.
Which index for an anniversary in October 2025
Belgian law (Civil Code art. 1728bis) reads the health index of the month BEFORE the anniversary: for October 2025, that is September 2025. The starting index is the one of the month before the lease was signed.
No intermediate rounding: the ratio is applied in full, then the result is rounded to the cent.
| Lease signed in | Starting index | Rent from October 2025 | Since signature |
|---|---|---|---|
| October 2024 | 132.41 (September 2024) | €1,021.52 | +2.15 % |
| October 2023 | 127.52 (September 2023) | €1,060.70 | +6.07 % |
| October 2022 | 124.92 (September 2022) | €1,082.77 | +8.28 % |
| October 2021 | 112.29 (September 2021) | €1,204.56 | +20.46 % |
| October 2020 | 109.78 (September 2020) | €1,232.10 | +23.21 % |
Before any regional correction. A lease indexed every year lands on the same figure whatever the path: the ratio always runs from the starting index.
What Flanders adds
Housing is regional. Three regions, three answers to the same question: does a poor energy certificate still weigh on the indexation of an older lease?
Between 01/10/2022 and 30/09/2023 Flanders indexed label D at 50 % and E/F not at all, and forbids catching up afterwards (decree of 3 October 2022, art. 4). Every later indexation is multiplied by a factor built from the health index of that frozen year. For a lease whose anniversary falls in this month:
Indexed in full, on the formula above. The only conditions left are the national ones: a registered lease, a certificate handed to the tenant, a written request.
Indexation is never automatic: it applies from your written request, and reaches back at most three months. An anniversary in October 2025 claimed late leaves money on the table for good.
An unregistered lease cannot be indexed, and neither can one whose tenant never received the energy certificate. Both are checked before the figure in the calculator.
Same month, other regions:
Figures as published by Statbel and read on September 30, 2026.
Your rent, your dates, the exact figure
The free calculator applies the formula, the regional correction and the three-month cap to your lease, and emails you the letter to send.
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