How are dividends from my Norwegian AS taxed when I live in Portugal?

Norway withholds tax at source on dividends to non-residents (treaty-reduced), and Portugal then taxes you as resident — with the outcome depending on your regime: IFICI can exempt foreign dividends, standard rules tax them at flat rates with credit for the Norwegian withholding. The order of operations at your move (when you emigrate vs. when you distribute) changes the result materially. Plan distributions around the move, not after it.