Ancillary expenses (Nebenkosten) are charges that are due on top of your base rent. They often include heating, water, trash collection, and building cleaning. Their exact amount depends on the dwelling and your consumption. The lease agreement lays out the ancillary expenses that you pay as well as the payment modalities. In most cases, these are prepaid as a lump sum each month together with your rent and then tallied and settled after year-end based on actual consumption.