Grundsteuer
によるポスト Frank (confidential) に ドイツ フォーラム
Ground tax (Grundsteuer) is collected by the twon council, due by regulation and no invoice is needed.
The procedure might vary by location, but where I live a statement of tax due and collection dates is sent to the property owner at the beginning of a calendar year. If you didn't receive it, you can probably ask the authority in charge for this information. Such official statements are often automatically generated documents without stamp or signature.