In order to legally reside in spain for more than 90 days you must become a Spanish resident.
There are various ways of obtaining residency depending on (a) your personal circumstances and (b) your country of origin (EU or non-EU). Similarly, anyone leaving Spain needs to officially renounce their residency.
Residency applications are processed at Extranjeria offices situated within the National Police headquarters. The nearest to Gaucín are in Ronda and Estepona and links to maps can be found at the foot of this page. Appointments must be booked online via this link - Proceso automático para la solicitud de cita previa:
Switch from green card to TIE (UK only)
Whilst both the residency green card and paper certificate of UK citizens are both still valid as proof of residency, it is advisable to swap this for the biometric TIE (tarjeta identidad Extranjeros). There are many reported instances of British residents having difficulties in dealing with official procedures and border crossings through not having the TIE card. For those who wish to swap to the TIE, the process is very straightforward and can be completed at the Extranjeria offices of the Policia Nacional in either Ronda or Estepona.
CAB Spain provide a useful guide https://www.citizensadvice.org.es/updating-your-green-certificate-for-a-tie-simple-steps/
UK citizens arriving by visa
Following the UK´s exit from the EU, all UK citizens entering Spain as residents with a visa must register for the TIE within 30 days of their arrival. If this is you, it is imperative that you book an appointment asap and then prepare the paperwork as directed in this guide:
EU citizens seeking residency
All EU citizens seeking residency and not from the UK are still required to prove Health and Wealth, amongst other documentation:
Abiding by residency rules
Becoming a resident has certain responsibilities, one of which involves managing your time out of Spain, especially during the first 5 years of legal residency. CAB Spain provide an excellent summary of the dos and don’ts:
Changing from resident to non-resident
If you find, for whatever reason, that you must return to your home country or move out of Spain to live and work elsewhere, then it is just as important to ensure you inform the authorities that you are officially leaving as it was when you arrived.
As a minimum you should:
• Inform your bank – you will need to change your resident account to non-resident
• Inform the town hall where you registered on the padron
• Go to the National Police office where the residency certificate was first issued and return your residency card.
When you cancel your residency at the National Police office they will issue you with a stamped document that includes the date of cancellation and the reason for it. This is your proof that you are no longer a resident and that you have informed the necessary people.
You will also have to let your fiscal representative know about your change in circumstances. You will probably still have to complete one more resident tax return the year after you leave Spain as taxes are presented retrospectively. After that you will complete a non-resident tax declaration form before 31 December for every subsequent year that you continue to hold property in Spain.