Product Handbook
Complete guide to using Grundwächter
Welcome to Grundwächter
Grundwächter is a free web tool that helps you quickly and easily verify your property tax (Grundsteuer) notice. The app recalculates your notice according to legal regulations and immediately shows you whether the tax authority has calculated correctly.
Who benefits from Grundwächter?
- Owners of residential properties (houses, apartments, plots)
- Landlords with one or more properties
- Anyone who wants to understand how their notice is calculated
- People considering filing an objection
Version 1 is completely free. All features are available without an account. An account additionally allows you to save your checks and deadline reminders.
What you need
To perform a check you need your Grundsteuer notice. Depending on your federal state, additional documents may be helpful.
| Federal state | Required documents |
|---|---|
| All except BY, BW, HH | Tax notice, property value notice (land value, floor areas) |
| Bavaria | Tax notice, plot area and building area |
| Baden-Württemberg | Tax notice, plot area, land value (Bodenrichtwert) |
| Hamburg | Tax notice, living area, location factor |
All values can be found on your Grundsteuerwertbescheid or Grundsteuermessbescheid. Pay attention to the correct unit (m², €/m², %).
Check step by step
The check is carried out in three steps. The progress bar at the top shows you how far along you are.
Step 1 – Select federal state
Select the federal state in which the property is located. The app automatically selects the correct calculation model.
Step 2 – Enter data
Enter the values from your notice. Which fields appear depends on the calculation model.
- Amount on notice (€) – the annual amount from the Grundsteuer notice
- Plot area (m²) – from the land register or notice
- Living area / building area – varies by model
- Land value (€/m²) – from your municipality's appraisal committee
- Assessment rate (%) – set by your municipality
- Year of construction – year the building was completed
Your entries are automatically saved in the browser. If you close the page, you can seamlessly continue the check later.
Step 3 – Evaluate result
The app shows you the calculated amount, the notice amount and the discrepancy – with a colour-coded assessment and a recommendation.
Calculation models
Since the Grundsteuer reform in 2025, Germany uses four different calculation models. Your federal state determines which model is applied.
| Model | Federal states | Calculation basis |
|---|---|---|
| Federal model | BB, BE, HB, HE, MV, NI, NW, RP, SH, SL, ST, TH | Land value + building value × tax rate × assessment rate |
| Bavaria model | BY | Plot and building area × equivalent figure × assessment rate |
| BaWü model | BW | Plot area × land value × tax rate × assessment rate |
| Hamburg model | HH | Living area × equivalent figure × location factor × assessment rate |
Federal model (12 federal states)
The property value consists of land value and building value. The tax rate (0.031% residential, 0.034% commercial) and the assessment rate are applied. Formula: property value × tax rate × assessment rate.
Bavaria model
Area-based model without considering the land value. Based on equivalent figures for plot and building area. Advantage: no market value assessment needed.
Baden-Württemberg model
Pure land value model. Only the plot area multiplied by the land value is taken into account – the building value is completely ignored.
Hamburg model
Living-area-based model. The living area is multiplied by an equivalent figure and a location factor. The location factor accounts for the location of the property in Hamburg.
Understanding the result
The result compares the Grundsteuer amount calculated by the app with the amount in your notice and shows the discrepancy.
Discrepancy levels
| Level | Discrepancy | Recommendation |
|---|---|---|
| No error | < €5 | Notice is correct. No action needed. |
| Minor discrepancy | €5 – €49 | Check inputs. Objection optional. |
| Significant discrepancy | ≥ €50 | Objection strongly recommended. |
Calculation steps
All calculation steps with formula, input values and intermediate result are shown transparently. Expand the detail view to follow every step.
Plain-language explanation
Below the result you will find an automatically generated plain-language explanation – for example: "The tax authority assumed a living area of 120 m², your input results in 105 m²."
The app works exclusively based on your inputs. Carefully check all entries against your original notice before filing an objection.
Generate an objection
In case of a significant discrepancy, you can generate a legally structured objection draft as a PDF directly from the app.
When is an objection worthwhile?
- Discrepancy of €50 or more
- Incorrect property data in the notice
- Wrong area figures or assessment rate
- When you have identified concrete errors in the calculation
Objection deadline
The objection period is 1 month after notification (§ 355 AO). For postal delivery the notice is deemed received 3 days after the letter date (§ 122 Para. 2 AO). If the deadline falls on a weekend or public holiday, it moves to the next working day.
The generated objection draft is a template and does not constitute legal advice. We strongly recommend having the draft reviewed by a tax advisor or lawyer before submitting.
Step by step
- Perform a check (result: significant discrepancy)
- Click "Generate objection"
- Enter your contact details and file reference number
- Review and adjust the justification if needed
- Download the PDF
- Send by registered mail to the responsible tax authority
- Keep the proof of postage
Deadline calculator
On the home page you will find a deadline calculator. Enter the date of your notice – the objection deadline is calculated instantly and automatically.
How the deadline is calculated
- Letter date of notice + 3 days = notification date (§ 122 Para. 2 AO)
- Notification date + 1 month = objection deadline (§ 355 AO)
- If the last day falls on Sat/Sun/public holiday → next working day
If the notice demonstrably arrived later, the actual delivery date applies. When in doubt, act earlier.
Dashboard & My checks
With a free account, Grundwächter automatically saves your checks and deadlines. The dashboard gives you an overview of all your checks.
What does the dashboard show?
- All saved checks with date, federal state, model and discrepancy
- Open objection deadlines with countdown (warning at ≤ 7 days)
- "Check again" link to repeat a saved check
- Button to start a new check
Creating an account
- Click "Sign in" in the header
- Select "No account yet? Register now"
- Enter email and password (min. 8 characters)
- Open the confirmation email and click the link
- Sign in and get started
Without an account, checks are not permanently saved – only in the browser. With an account, all checks are accessible across devices.
Privacy & your data
Grundwächter only processes the data necessary for the app to function. The application complies with GDPR requirements.
Data stored at a glance
| Data | Without account | With account |
|---|---|---|
| Check inputs | Browser (localStorage) | Encrypted database |
| Check results | Browser (localStorage) | Encrypted database |
| Objection deadlines | Not saved | Encrypted database |
| Email address | Not collected | Login & reminders only |
Your GDPR rights
- Access & export: Profile → Export data (JSON download of all saved data)
- Deletion: Profile → Delete account (deletes all data irreversibly)
- Correction: By repeating the check with corrected values
Further information can be found in our Privacy Policy (link in the footer).