Tax assessment from the Finanzamt
A Steuerbescheid (tax assessment) tells you how much tax you must pay or will get back. It usually comes from the Finanzamt.
What you can do
If you disagree, you can file an Einspruch.
Say which Bescheid your Einspruch is against, and sign it.
File the Einspruch in time, even if some documents are still missing. Keep proof that it arrived.
If you do nothing, the Bescheid usually becomes final when the deadline ends.