Hmm - so correct me if I'm wrong -
Denmark and Sweden give no credit for having paid tax in Portugal.
The Uk says OK, you've paid tax in Portugal but you'll have to pay us the extra to make it up to our tax level. (Or is it PAYE with a UK Netjets office)?
Spain says you've paid tax in Portugal so we're no longer interested in taxing you. Whereas France used to say this, now they say they want full French tax.
And obviously living in Portugal, you just have to pay their tax. Presumably you also have to pay this is you live in a tax free area such as Andorra or Monaco.