183-days rule is NOT a thing in germany for corporate taxes, and I think it is not in income taxes either. It may be an indicator, but it is not a hard proof. Important is, where you have your social life set up ("Lebensmittelpunkt"). That is, you can reside more than 183 days abroad, but if you have a family, golf club membership, permanent residence, your stock brokerage account etc. still in germany, you still count as a german tax resident. There are no hard laws with X days around it, german law revolves a lot around that "Lebensmittelpunkt" which will be decided on a per-case basis.