If you are not a resident of the EU, you need to consider sticking to the assistance of the tax representative in Portugal. He will do all the necessary work for you, and you will be able to get your NIF which is a Portuguese tax number.
Besides, you can think about working with an intermediary that specializes in services of this kind. They will suggest you the guidance of a tax representative and proper help that is required in order to receive NIF. And, you will not have to bother about anything at all!
The only thing that is required from you is getting the documents ready. The list of them is not too great. This is what you need to prepare beforehand:
- A scan of your passport;
- Proof of address (a utility bill is about to be fine in this case).
Then, you will have to submit an application, and proceed with paying a fee. This is basically all you will be involved in. The last thing you need to note is as follows: just wait for a few days, and your NIF will be sent to you. Such a way turns out to be really fast by the way. Good luck!