No, once you’re assigned a NISS, it remains the same for life. It doesn’t require periodic renewal. Related ArticlesWhy do you need a NISS in Portugal?How to correct/update your name on Portal das FinançasDo I need a tax representative in Portugal if I'm an EU/EEA resident?What documents do I need to apply for a NISS?When Should You Choose a NIF with 1-Year Tax Representation or Automatic Renewal?