Do I need to declare foreign bank accounts in Germany?

Germany taxes the worldwide income of its tax residents, and that very much includes income from accounts you hold abroad. The accounts themselves don't need to be "registered" with German authorities, but the interest, dividends and any realised capital gains generated in them belong on your annual tax return — usually on Anlage KAP for capital income, and possibly Anlage AUS for foreign income.

A common assumption is that foreign banks simply don't communicate with the German tax office. That hasn't been true for years. Under the EU's Common Reporting Standard (CRS) and various bilateral data-exchange agreements, banks in more than 100 countries automatically report account data on their foreign tax residents to the relevant home authority — and the German Finanzamt receives data from most of these countries. They then cross-check against your filed return. So the practical risk of "forgetting" a foreign account is much higher than people tend to assume.

The cleanest approach is also the simplest: write down every account you hold outside Germany, note the income each one generated during the year (interest, dividends, gains), and include it all on your German return. For the first year of doing this, a Steuerberater who handles cross-border cases regularly is usually well worth their fee — they will know which forms apply to which income and how to credit any foreign tax already paid.