Moving to Germany to take up two jobs, but will need two homes. I've heard the costs for the second home may be tax-deductible. Under what conditions?

Question

Consider the situation in Can I register a Nebenwohnung before I have a Hauptwohnung?:

Suppose that married persons X and Y are moving to Germany. They will share a Hauptwohnung (primary residence) in city A, but X will additionally occupy a Nebenwohnung (secondary residence) in city B because X has a job at the other end of the country. So far so good: both will register as Hauptwohnung in city A, and X will additionally register as Nebenwohnung in city B.

I've heard that under certain circumstances, they might be able to deduct (some of the) costs for the Nebenwohnung that X occupies several days per week, from income tax — and perhaps the travel costs, too. For example, see Haupt- und Nebenwohnsitz: Rechtlichte Regelungen, which states, among other things:

Wird der Zweitswohnsitz nur aus berüflichen Gründen genutzt, besteht die Möglichkeit, die doppelte Haushaltsführung steuerlich geltend zu machen.

(...)

Wer steuerlich befreit werden will, muss mindestens 10% der Steuern, die auf den Hauptwohnsitz fallen, selbst bezahlen.

It's not clear to me what those conditions mean in practice. I'm not familiar with German legalese. For example:

When they say aus berüflichen Grunden, would that include that the second job is simply too far away, or does it mean for business purposes only? I read something about Betriebsausgabe vs. Werbungskosten but it's not clear to me if it can be deducted in either case or only if it counts as a Betriebsausgabe. In our case it wouldn't, because X and Y are both employees (both are Beambte, in case it matters).

And on the payment of the taxes for the Hauptwohnsitz. Are they talking about real estate taxes? Does that imply X and Y must own the Hauptwohnung in city A, or do tenants pay those taxes themselves too and would this condition not pose any problems?

It is useful to know this in advance, for it may be financially more advantageous to have a single shared primary residence together where only one person travels back and forth weekly, compared to a more symmetric situation where both travel back and forth fortnightly, as we did in the past in England.

Answer 1

The second job being "too far away" is enough. My Nebenwohnung in Zürich is only 80 km from my Hauptwohnung in Germany, and the rent is entirely tax-deductible in Germany.

I don't know what the 10% rule is about, but I strongly suggest you get a tax adviser (Steuerberater(in)). The UK income tax system is relatively straight-forward. Doing it yourself is entirely practical. In contrast, the German tax system is very complex. I had an acquaintance who (among other things) had held a job advising companies on international VAT regulations (so she wasn't afraid of bureaucracy); she was a native German speaker; she had started the training to become a tax advisor. She didn't do it herself.

It costs us a few hundred euros each year (tax deductible of course), and it is based on your (family) income. If you can't get recommendations from your new employer, ours is a member of VLH, and there will be a member near you.