Nebenkosten App is a software for operating cost statements available on iOS, Android, and web browsers. It guides landlords through a workflow covering tenant info, accounting periods, payments, distribution keys, cost items, and meter readings, ensuring all data is captured. The software generates professional PDFs with itemized cost breakdowns, diagrams, CO₂ reports, and signature fields, which can be printed, emailed, or shared via links. An AI system reviews statements for completeness and inconsistencies before PDF creation. Supporting various property types, Nebenkosten App offers cloud synchronization and stores statements in a write-protected archive. It complies with DSGVO and allows secure JSON data exports. The platform includes templates for regional regulations like German BetrKV, Austrian MRG, and Swiss rental laws. Automated calculations manage CO₂ cost allocation and heating adjustments per legal frameworks.