Since January 1, UK nationals not registered as Spanish residents can only stay in the country for up to three months out of every six.
Britons have been advised to register for healthcare as residents in Spain and have until June 30, 2021 to change their driving licences to Spanish ones.
Henny Illingworth, an estate agent, has been living in Malaga for almost four years and feels uncertain about the future.
"Previously, as an EU citizen in Spain, I had the right to be here and now I just have permission to stay. It does feel a big difference and it feels that there has been a huge amount of uncertainty and misinformation over the last few years. It leaves us feeling like: 'Am I safe? Am I stable here?' It's not a very nice feeling to live with."
It's also a worrying time for Kirsty Ridyard who's the Director at Phoenix College in Mala, a sixth-form college based on the British education system.
"Personal and professionally it is going to affect me. Professionally, we cannot get the products that we need to teach chemistry effectively in Spain because they are sourced in Britain and those are so expensive over there now, it's going to be prohibitive.
"And personally, I just don't know what's going to happen with the transport. It used to be like hopping on a bus getting on a plane to go to London and getting back, for me and my family, who are still there. But now, we just don't know if we are going to need visas or not."
And for Spanish students wanting an education in the UK, the new rule is proving problematic. Victoria Rincon, 18, is now thinking about going to university elsewhere.
"I have applied (to universities) in England, but I don't think I will not go because the fees are too high. And I think that is what is happening to a lot of people in Europe. We are going to miss their education in England because of the price. And then, I think I'm going to the Netherlands."
There are around 360 thousand British residents registered in Spain.
Life after the COVID-19 pandemic should see tourists return but there could be fewer Brits living there by then.