Is Your Indexmiete Increase Correct? How to Check (2026)
Is Your Indexmiete Increase Correct? How to Check
Old rent × (current CPI ÷ base CPI), and the increase does not happen automatically.
The landlord must declare it in text form, stating the old and new index figures and the new rent in euros (§ 557b Abs. 3 BGB). Miss any of those and the increase is ineffective.
§ 557b Abs. 3 BGBIn 60 seconds
The increase does not happen automatically: the landlord must declare it in text form, stating the old and new index figures and the new rent in euros (§ 557b Abs. 3 BGB).
The base CPI is the figure at the last setting. At signature or the last adjustment; both figures must rest on the same base year (currently 2020 = 100).
The percentage applies to the net rent; Nebenkosten are untouched. The monthly figure governs, not the annual average, unless the contract says otherwise.
The rent must stay unchanged for at least twelve months between adjustments (§ 557b Abs. 2 S. 1 BGB). Where the landlord waits longer, they may claim the accumulated rise at once.
You owe the higher rent only from the start of the second following month after the declaration arrives (§ 557b Abs. 3 S. 3 BGB); unlike § 558 BGB, no consent is required.
What the law says
A change of rent under an index agreement must be asserted by declaration in text form, stating the change in the price index that has occurred and the respective rent or the increase as a sum of money. The changed rent is payable from the start of the second month following receipt of the declaration. Working translation; the German original is the binding text.
A worked example
A net rent of €900, last set at an index figure of 119.8.
€900 × (125.2 ÷ 119.8) = €940.57. The percentage is (current CPI ÷ base CPI × 100) − 100. Check which figure applies with the Federal Statistical Office.
What does not apply to an index rent
| Rule | Applies to an index rent? |
|---|---|
| Cap of 20% / 15% over 3 years (§ 558 Abs. 3 BGB) | No (§ 557b Abs. 2 Satz 3 BGB) |
| Tied to the local comparable rent / Mietspiegel | No |
| Tenant's consent required | No |
| Rent brake on the starting rent (§ 556d BGB) | Yes: at the start of the tenancy |
A modernisation pass-on under § 559 BGB is permissible only so far as the landlord is not responsible for the modernisation (statutorily mandated works, for instance).
A planned reform ("Mietrecht II") would cap index increases in tight housing markets. As at June 2026 that is a draft and not in force: check the current position before paying.
What it means for each side
- Check the declaration names both index figures and the new rent in euros.
- Check that twelve months separated the two adjustments.
- Pay only from the second month after receipt.
- Make sure both index figures use the same base year.
- Declare in text form with both index figures and the new rent in euros.
- Observe the twelve-month interval.
- Apply the percentage to the net rent only.
- Use the monthly figure, not the annual average, unless the contract says otherwise.
Common mistakes
Miss the old or new figure, or the new rent in euros, and the increase is ineffective.
Both must rest on the same base year, currently 2020 = 100.
It is owed only from the start of the second month following receipt.
It applies to the net rent; Nebenkosten are untouched.
What to do next
Find the base CPI from the contract or the last adjustment.
Check the current monthly figure with the Federal Statistical Office: same base year.
Calculate: old rent × (current CPI ÷ base CPI).
Check the twelve-month interval and that payment starts in the second following month.
Frequently asked questions
How do I calculate my Indexmiete?
The new rent is: old rent × (current VPI ÷ base VPI). The base VPI is the Verbraucherpreisindex of the Statistisches Bundesamt at the time of the last setting, the current VPI the level at the increase. Both on the base 2020 = 100. Example: 900 € × (125.2 ÷ 119.8) = 940.57 €. What matters is the percentage change of the index, applied to the most recently agreed Nettokaltmiete (net cold rent) under § 557b Abs. 2 BGB.
How often can the Indexmiete be increased?
At most once a year. After each adjustment the rent must stay unchanged for at least twelve months (§ 557b Abs. 2 Satz 1 BGB). An increase has no retroactive effect, but if the landlord has not raised the rent for longer than a year, they may claim the accumulated index rise in one step.
From when do I have to pay the increased Indexmiete?
Only from the start of the second month after the increase declaration reaches you (§ 557b Abs. 3 Satz 3 BGB). If the declaration arrives in June, you pay the new rent from August. You owe nothing extra before then, even if the index rose long ago.
Does the Kappungsgrenze or the Mietspiegel apply to an Indexmiete?
No. The Kappungsgrenze (cap on rent increases) of 20 % over three years under § 558 Abs. 3 BGB expressly does not apply to the Indexmiete (§ 557b Abs. 2 Satz 3 BGB). There is also no binding to the ortsübliche Vergleichsmiete (local comparable rent) or the Mietspiegel (rent index table). Only the VPI matters. A 3.5 % per-year cap in strained housing markets is, however, planned from 2026 (see below).
What must the increase declaration contain?
It must be in Textform (text form, email is enough) and state three things: the VPI change that has occurred (old and new index level) and the new rent or the increase as a euro amount (§ 557b Abs. 3 Satz 2 and 3 BGB). If any of these is missing, the increase is invalid (BGH, judgment of 22 November 2017, Az. VIII ZR 291/16).
Can the Indexmiete also go down?
Yes. With the Indexmiete the rent changes with the VPI, so in both directions (§ 557b Abs. 1 BGB). If the index falls, the rent can fall accordingly. A clause allowing only increases puts the tenant at a one-sided disadvantage; any agreement deviating to the tenant's detriment is invalid (§ 557b Abs. 5 BGB).
This page gives general information as at the date shown. It does not replace legal advice on an individual case.