I'm in Catalonia, Spain (for a few more weeks) and do not recommend. I don't know what you are making, but I am also an Autonomo, and I'm being royally fucked on social insurance and taxes. My tax and SI bill for this year will be around 60%, and fuck that. And yes, I have tried different accountants. Essentially, the tax department decided that a lot of my expenses are not allowable, and because I have bank accounts in other EU countries as well as Spain, they decided that I am "probably hiding something" (their words). I can go and spend a lot of money on lawyers, or I can just pack up and leave.
Combined with the bullshit Catalan independence movement and accompanying social and economic instability, generally unfriendly Catalans, terrible quality of food (essentially salt, with a hint of whatever it claims to be on the package), and the "we will bill you whatever the fuck we want, good luck clawing your money back" utilities (literally opened a 400 EUR bill from the phone company 10 minutes ago), I am totally done with this place.
I have lived in many countries, and all places have challenges and ups and downs. This place, however, is the pits.
Spain does the same thing as Portugal, for company workers, where they "hide" part of the social security payment from payment receipts. Companies pay 23.6% and the worker 4.7%. Only the latter appears in the salary receipt, the other is a company expense.
Edit - it's 29.3% of the base mínima de autónomos - which is about 920 euros a month. Now, I honestly have no idea what that actually means, but it means you pay about 270 euros regardless of what you earn (it's a stupid system that benefits the well-off).
To the OP: Did you visit Portugal? Why do you want to move there?
It is not a third-world dump hole but it is a not a first world class country either.
Within the EU you can transfer social security between countries. If he doesn't he will be entitled to retirement income when reaching retirement age. In no condition would he forfeit these payments.
> It is not a third-world dump hole but it is a not a first world class country either.
One of the best health services in Europe, one of the lowest crime rates in the world, lots of english-speaking nationals, and gorgeous weather. You won't find the hubbub of very large cities such as NY, Paris, or London, but then again you might not miss the hubbub. It's definitely first-world.
I'd be interested in hearing what it is that you find in first-world countries that you don't find in Lisbon. Genuine question.
Then, you'll have a few options. If the remote company has no Portuguese subsidiary, you'll have to operate as an independent contractor (trabalhador independente) or as a one person company (sociedade unipessoal). It's basically the same, except as a company you must have an accountant. As an independent contractor you may have an accountant, or you may choose a simplified accounting model where you don't declare expenses, and your profit margin is estimated by the fiscal authority.
Income tax is progressive. You should be able to read the brackets here: https://economiafinancas.com/2017/escaloes-irs-2018/
You declare your income in May, and pay income tax in July/August.
Social security is a fixed rate: 29.6%. It is a mandatory retirement savings, and provides disability income should you require it. You pay social security quarterly or monthly.
Access to the national health service is not dependent on any tax or regular payment. You don't need health insurance.
As an independent contractor, you would pay VAT, but cross-border transactions are exempt, so your VAT is probably zero (check this with an accountant; EU's rules on cross border transactions are in flux).
References:
https://www.portaldocidadao.pt/
http://www.portaldasfinancas.gov.pt/