Your NIF (Número de Identificação Fiscal) is genuinely the first thing to sort out in the entire Portugal process — you need it for the D8 visa application itself, plus your bank account, rental contract, phone plan, and business registration.
Before you arrive (remote route)
Non-residents can’t self-serve online — you appoint a fiscal representative in Portugal via power of attorney, who submits the request through Portal das Finanças. Typical turnaround from a commercial provider: NIF confirmed in 3–5 business days. The NIF itself is free from the government; providers charge a service fee (one example: €79–€249 depending on speed, plus ~€99/year for ongoing representation until you’re tax resident).
Once you’re in Portugal (in-person route)
Go directly to a Serviço de Finanças (tax office) or Loja do Cidadão by appointment — free, no fiscal representative needed. Bring your passport/ID (with your entry visa, if applicable).
NISS (social security number)
Requested through the same official process — required documents differ by citizenship, and it also needs proof of your work relationship (contract, self-employment registration, or “digital nomad contract”). Also free.
Official source: gov.pt — Como pedir o NIF e o NISS
Next step: with your NIF in hand, apply for the D8 visa if you haven’t already, and start looking at bank account options — several banks want your NIF before they’ll open an account.