If you want to contest an incorrect tax assessment in Germany, you must...

1. do nothing.
2. throw the notice away.
3. file an objection. ✓
4. wait until another notice arrives.

If you believe your tax assessment is wrong, filing a formal objection (Einspruch) ensures your taxes are calculated fairly and correctly. Many people in Germany use a 'Steuerberater' (tax advisor) to help them navigate these precise rules!