Portugal uses acronyms everywhere. When you move to Porto, it can feel like every useful thing has been shortened into three or four letters: NIF, NISS, AIMA, SNS, IMT, AT. At first it is annoying. After a while, you start using them too.
I would not try to memorise every acronym at once. Learn the ones that affect daily life first, then keep the rest for when they appear in a form, email or appointment.
NIF
NIF means Número de Identificação Fiscal. It is your Portuguese tax number.
You need it for many normal parts of life: bank accounts, leases, utilities, contracts, invoices, property, phone plans and tax matters. A NIF is one of the first numbers most newcomers deal with, but it does not solve everything by itself.
NISS
NISS means Número de Identificação da Segurança Social. It is your Social Security identification number.
You may need it for employment, self-employment, contributions, certain benefits and Social Security access. Foreign citizens can request it online through Social Security, and people with a Portuguese Citizen Card normally have it assigned automatically.
AIMA
AIMA means Agência para a Integração, Migrações e Asilo. It is the agency involved in many immigration, residence, integration and asylum matters.
AIMA took over many administrative migration functions after SEF was restructured. If you are dealing with residence permits, renewals, family reunification or migration appointments, AIMA may be part of the process.
SEF
SEF was the Serviço de Estrangeiros e Fronteiras. You will still hear people say “SEF” because the old name is stuck in everyone’s head, but the system changed in 2023.
If an old blog, Facebook post or forum comment tells you to contact SEF, check what the current AIMA or police-border process is instead. Old immigration advice in Portugal can go stale quickly.
CRUE
CRUE means Certificado de Registo de Cidadão da União Europeia. It is the EU citizen registration certificate.
EU, EEA, Swiss and Andorran citizens who stay in Portugal for more than three months normally request this registration certificate through the Câmara Municipal where they live. It is not the same as a non-EU residence permit.
AT or Finanças
AT means Autoridade Tributária e Aduaneira. Most people just say Finanças.
This is the tax and customs authority. You deal with it for NIF matters, fiscal address, IRS, IVA, invoices, IMI, IUC, customs and many tax-related questions. The online portal is Portal das Finanças, and having access to it matters a lot once you live here.
IRS
IRS is Portugal’s personal income tax. It is not the American IRS, even though the name confuses people.
If you are tax resident in Portugal, work here, are self-employed, have rental income, pensions, foreign income or other reportable income, IRS can matter. The normal annual declaration period is from 1 April to 30 June for income from the previous year.
IVA
IVA is VAT, value-added tax. You see it on invoices, receipts and business paperwork.
If you are self-employed or running a company, IVA is something to understand before invoicing. Whether you charge it, do not charge it, or fall under a particular regime depends on your activity and turnover.
IMI
IMI means Imposto Municipal sobre Imóveis. It is the municipal property tax paid by property owners.
If you rent, IMI is usually not your tax to pay directly. If you buy property, it becomes part of the yearly cost of owning a home in Portugal.
IUC
IUC means Imposto Único de Circulação. It is the annual vehicle circulation tax.
If you own a car or certain other vehicles in Portugal, check IUC in Portal das Finanças. In 2026, the usual rule is still payment during the vehicle’s registration month for most vehicles, but the system is changing, so use the official portal rather than memory.
SNS
SNS means Serviço Nacional de Saúde, Portugal’s national health service.
If you live in Portugal, SNS access may matter depending on your residence status, work, nationality and paperwork. Keep your health documents, user number and prescriptions organised.
SNS 24
SNS 24 is the national health advice and triage service. The phone number is 808 24 24 24.
It can help with non-emergency health questions and where to go next. It is not the emergency number. For a real emergency, call 112.
IMT
IMT means Instituto da Mobilidade e dos Transportes. It deals with transport, driving and vehicle matters.
You may meet IMT when dealing with driving licence exchange, vehicle inspection, car registration questions, professional transport matters or imported vehicles.
DUA
DUA means Documento Único Automóvel. It is the vehicle registration certificate.
It identifies the vehicle and allows it to circulate on public roads. It includes details such as the vehicle, registration and owner information, and it replaced older separate vehicle documents.
IEFP
IEFP means Instituto do Emprego e Formação Profissional. It is Portugal’s public employment and professional training institute.
Job seekers, employers, training programmes and some work-support routes may involve IEFP. Some residence or employment situations may also ask for IEFP-related documents or registrations.
ACT
ACT means Autoridade para as Condições do Trabalho. It is the authority for working conditions and labour inspection.
If you need official information about employment rights, contracts, workplace safety or employer obligations, ACT is one of the places to check.
DGES
DGES means Direção-Geral do Ensino Superior. It deals with higher education matters.
You may meet DGES if you need recognition of foreign higher-education degrees or diplomas in Portugal. Degree recognition has different types, so do not assume one process fits every situation.
DGAV
DGAV means Direção-Geral de Alimentação e Veterinária. It deals with food and veterinary matters.
If you move with pets, travel with animals, deal with animal health paperwork or certain food-sector issues, DGAV can appear.
ANEPC
ANEPC means Autoridade Nacional de Emergência e Proteção Civil. It is the national civil protection authority.
It matters for emergency coordination, civil protection information, major incidents, preparedness and wildfire-related information.
IPMA
IPMA means Instituto Português do Mar e da Atmosfera. It is Portugal’s weather, sea, climate and atmospheric institute.
You will see IPMA when checking weather warnings, sea conditions or rural fire danger. It is especially useful in summer, during storms or if you travel outside the city.
IRN
IRN means Instituto dos Registos e do Notariado. It handles many registration and notary-related services.
IRN can matter for civil registration, nationality, property registration, commercial registration, vehicle registration and official certificates.
CTT
CTT is Correios de Portugal, the postal service. You may use CTT for letters, parcels, registered mail, notices and some payment or service points.
Do not ignore registered mail in Portugal. Some important official notices still arrive by post, and missing them can create problems.
AL and RNAL
AL means Alojamento Local, the short-term accommodation category used for many tourist rentals.
RNAL means Registo Nacional de Estabelecimentos de Alojamento Local. It is the national register for local accommodation, available through the national tourism register system. You may see RNAL numbers on legal short-term rental listings.
The ones I would learn first
If you are new in Porto, learn these first: NIF, NISS, AIMA, CRUE, AT, SNS and IMT. Those are the ones most likely to affect your first months.
The rest can wait until they enter your life. They will, but no need to invite all of them on day one.
