A NIF is essential for anyone who lives in Portugal.
You will need it to carry out essential tasks such as opening a bank account or renting an apartment.
Basically, you need a NIF for any sort of official transaction in Portugal.
Here are some examples:
Opening a bank account
Renting property long-term
Buying or selling property
Setting up utilities (water, gas, electricity)
Signing a mobile phone contract
Applying for a mortgage or other forms of credit
Enrolling in a school
Getting hired in Portugal and receiving your salary
Receiving social security payments and other benefits in Portugal
Filing and paying taxes in Portugal
Buying a car
Applying for a driver’s license
Inheriting Portuguese assets
At the time of this writing, some consulates require that applicants have a NIF before submitting their residence visa application.