Rent indexation in Flanders, January 2025
Your lease has its anniversary in January 2025? Here is the health index to use, the formula, and what Flanders adds on top.
Which index for an anniversary in January 2025
Belgian law (Civil Code art. 1728bis) reads the health index of the month BEFORE the anniversary: for January 2025, that is December 2024. 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 January 2025 | Since signature |
|---|---|---|---|
| January 2024 | 129.53 (December 2023) | €1,032.42 | +3.24 % |
| January 2023 | 127.89 (December 2022) | €1,045.66 | +4.57 % |
| January 2022 | 115.60 (December 2021) | €1,156.83 | +15.68 % |
| January 2021 | 109.88 (December 2020) | €1,217.05 | +21.71 % |
| January 2020 | 109.18 (December 2019) | €1,224.86 | +22.49 % |
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 January 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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