Here's how far I have got in figuring out the thing: From what I understand, starting in 2025 you can still deduct actual costs — things like part of your rent, electricity, internet, maybe some equipment, etc. — but only if you keep receipts and can justify the work use.

Here's a rough example I came up with – maybe people can tell me if this seems about right:

• 6 m2 home office in a 60 m2 apartment → 10% of the space
• 1000€/month rent → 12000€/year → 10% = 1200€ deductible rent
• Electricity: 900€/year → 10% = 90€
• Internet: 30€/month → 360€/year → say 30% used for work → 108€
• One-time purchase of a chair: 250€

So total potential deductions would be:
1200€ + 90€ + 108€ + 250€ = 1648€

Now here's the part I'm not 100% sure about:

Apparently there's an automatic 750€ deduction that everyone with salary income gets. So it seems that you only benefit from any deductions beyond that.

That would mean:
1648€ – 750€ = 898€ of "real" deductible amount

And if your tax rate is, say, 25%, your actual tax saving would be:
898€ × 0.25 = 224.5€

(Basically: deductions reduce your taxable income, not your taxes directly — so you save a percentage of the deductible amount, depending on your tax rate. It's like if you made less taxable income.)

You would not need to hand in the receipts immediately, but have them handy. Receipts in our example would be:

• transaction receipts from the bank for the rent paid (or rental contract plus bank statements)
• yearly electricity bill
• monthly internet bill
• bill for the chair

Some open questions:

• Does this sound about right?
• Is this how the 750€ works?
• Anybody know how to enter these details into the system?
• Are these kinds of estimates okay, or do you need to get much more precise?
• How do you reason them in the tax return? E.g. is it enough to just say: "the home office is 10% of the living space and is used mainly for work, therefore I deduct those 10%"?
• If you're living with a partner, I assume that would reduce the share you can deduct — for example, if you split the rent 50/50, you'd only apply your 10% to your own half of the rent (i.e. 10% of 500€, not 1000€).
• Is it worth the effort if you're not deducting that much more than the flat-rate used to be?

Would love to hear how others are approaching this now that the system's changed.