Calculating an Indexmiete: is the increase right?
How to check an Indexmiete (index-linked rent) increase yourself: the sum with the consumer price index (CPI), the form and the timing.
The new rent is right if it equals the old rent × (current CPI ÷ base CPI). Also check that the increase came in text form and states the old and new index figures and the new rent in euros.
How to check an Indexmiete increase
You only need two index figures and your current rent. You can check everything else in the letter itself.
- 1
Find the base CPI
The base CPI is the starting figure. You find it in your lease or in the last adjustment letter.
- 2
Look up the current CPI
The Statistisches Bundesamt (Federal Statistical Office) publishes the CPI every month. Make sure both figures use the same base year.
- 3
Do the sum
The formula is old rent × (current CPI ÷ base CPI). For example, €900 × (125.2 ÷ 119.8) = €940.57.
- 4
Check the letter
The increase must come in text form. The letter must state the old and new index figures and the new rent in euros.
- 5
Check the 12-month gap
At least twelve months must pass between two increases.
- 6
What the increase applies to
The increase applies to the net rent only.
Why this matters
Under § 557b Abs. 3 BGB, the landlord must declare the change in text form. The declaration must state the change in the index, and the new rent or the increase as a sum of money. You pay the new rent from the start of the second month after the declaration reaches you.
General information, not legal advice.
Frequently asked questions
From when do I have to pay the increased Indexmiete?
You pay the increased Indexmiete from the start of the second month after the landlord's declaration reaches you (§ 557b Abs. 3 Satz 3 BGB). If it arrives in June, you pay the new rent from August.
Can the Indexmiete also go down?
Yes, the Indexmiete moves with the CPI in both directions (§ 557b Abs. 1 BGB). A clause that only allows increases is invalid (§ 557b Abs. 5 BGB).
Does the cap on rent increases apply to an Indexmiete?
No, the cap on rent increases does not apply to an Indexmiete, and neither does the Mietspiegel. Only the CPI counts (§ 557b Abs. 2 Satz 3 BGB).
Also in this topic: Mietpreisbremse check: are you paying too much rent?How to read and use the Mietspiegel as a tenantModernisierung: tenant rights & rent increaseAll guides: Rent & rent increases
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