How do **Nebenkosten** (additional costs) work in a German rental contract?

In Germany, the Nebenkosten (additional costs or utility charges) listed in your rental contract are usually an estimated advance payment. At the end of the year, your landlord calculates the actual expenses for things like heating, water, and garbage collection. They then compare this total to the advance payments you've made throughout the year. This means you might either need to pay an additional amount or receive a refund. If you ever suspect there's an error in the calculations, it's a good idea to seek legal advice.