Moreover, note that any Portuguese citizen resident in Portugal can serve as your tax rep. One of my friends was happy to help me out by serving as my tax rep and saving me a few bucks. Drinks are on me.
For a typical non-resident, the tax rep’s obligations are negligible. Once a year he receives my property tax bill and hands it over to me when convenient, but I can also download this online, and my IMI bill is set for autopay from my Multibanco account anyway. He’s not on the hook to pay my taxes.