Illustration generated for this guide. It does not represent a property for sale.
Start with the documents, not the result
When seeking a new rent amount, it is tempting to begin with a calculator. A better first step is collecting the contract and relevant information: region, lease type, dates, reference rent and documents needed for checking. Mark missing information as missing. A precise calculation based on the wrong date is still wrong. The quality of the file comes before the quality of the result.
What Proprioo announces
Proprioo presents indexation calculations and letter preparation for ordinary main-residence leases in Belgium’s three regions. This does not mean every contract and situation is covered. Use a simple fictional file for your trial and read the interface guidance. Check the service’s scope when you use it. Do not apply a result to another lease type without verification.
Prepare your next step: Tenants and leases: keep your files separate and clear
Check each input
Prepare a separate checklist. For each value, identify its source: signed contract, certificate or official resource. Verify indices and conditions relevant to your situation with the competent resources. Rules can change and have regional particularities. This article therefore supplies neither a universal formula nor a rate to copy. If your file contains an ambiguity, seek verification before using the result in communication with a tenant.
Read the letter as a consequential document
A tool-prepared letter deserves the same review as one written manually. Check the people, address, contract references, amounts and dates. Ensure the request matches your real circumstances. Keep the information explaining your calculation. An attractive document does not make a request correct. In a disagreement, you will need to explain the facts and applicable rules.
Test without a real file
Proprioo’s public version is described as a demo using local browser storage. Do not enter real personal information merely to explore it. Use a fictional example and compare the steps with your own checklist. Before operational use, check terms, backups and availability. The tool’s value lies in structuring your work while retaining human verification of the decision.
Sources and references
ComparImmo editorial team. Sources checked on 3 October 2026. Check the rules for the region and your circumstances before making a commitment.