Following the UKs departure from the EU, UK passport holders are now Third Country Nationals and therefore must adhere to the rules of stay in Europe within the Schengen limits. These rules have been in place for decades and are nothing new except for the fact that they now apply to UK passport holders as well as all other Third Country Nationals such as Russians, Chinese, Venezuelans etc.
Non-Residents i.e. tourist who do not hold either of the above and are visitors using a UK passport are governed by the 90 days in any 180 days rule. There are Schengen calculators available here https://www.schengenvisainfo.com/visa-calculator/ which can be used to monitor stays and visits, bearing in mind that both travel days are included in the 90 stay days.
This means for a UK Passport holder who is Non-Resident in an EU country, regardless as to whether they may own property and/or a vehicle in Spain, are restricted to 90 days stay in any 180 days, this a rolling period. For those people who were known as “Swallows” and were used to spending 6 or more months (not necessarily consecutively) in Spain in their own property or indeed in rented property, this is no longer a possibility unless they wish to apply to become Residents via a Non-Lucrative or Golden Visa. By doing this they would be declaring that they are RESIDENTS in Spain and therefore would be liable to pay tax in Spain. This is not a “way around” the 90-day limit but a life choice.
Any Swallows who had previously held a Green Residencia (Certificado de residencia de ciudadano de la unión) or indeed obtained a TIE card whilst not ACTUALLY being resident will now fall foul to NHS cover in the UK. This is due to the fact that having registered an S1 in Spain for health cover they declared that they were resident in Spain and no longer required cover in the UK. Also, they would have needed to present an annual Tax Return in Spain and as most haven’t Hacienda WILL catch up with them, albeit a few years down the line and the individual is then faced with, generally a rather larger tax bill.
People are now aware, that passports are stamped on entry and exit from Spain, and this is one method of control (available to Immigration) of checking that travellers have not exceeded their 90-day limit if not resident and that those with temporary TIE have not exceeded the limits outside Spain which could mean that their residency status could be revoked.
This is important because of the rules on how long a foreign resident can be absent from Spain without losing their residency status and hence their rights under the Withdrawal Agreement.
If you have been legally resident in Spain for fewer than five years your status may be affected if you are absent for six months or more in one year. There are some exemptions to this rule where one single absence of 12 consecutive months may be permitted, for reasons such as pregnancy and childbirth, serious illness, study or vocational training, but these are exceptions.
In order to know the maximum time you can be out of the country as a holder of a temporary residence document (a green certificate that DOES NOT have the words “permanente” on it or a TIE with a 5 year validity) you must take into account two different conditions
Most importantly you must not be outside Spain for more than a total of 6 months within a period of one calendar year. In the case of more than one departure in your first five year period the total of the time spent outside Spain cannot exceed 1 year (365 days). As an example in your first year you spend 45 days outside of Spain, in your second year you spend 95 days outside of Spain and in your third year you spend 60 days of of Spain this would mean that in your final two years you could only be absent from Spain for a maximum of 165 days.
If you comply with these two requirements, you may keep your residence card and renew it (as long as you comply with all the other renewal requirements, which are different according to the type of residence).
All the above information is shown in: Article 162.2 of Royal Decree 557/2011
From the 1st of January 2021 staying in Spain longer than the 90 days allowed at a time with a green certificate of residence, would be allowed, BUT if they “disappear” for 6 months or more in a calendar year in order to avoid paying tax in Spain, they will then fall foul of the loss of residency status rules and the green certificate or newly obtained TIE card can be revoked.
Once the British national is a permanent resident in Spain (i.e. resident for 5 years or more), the Withdrawal Agreement states that their residency right will only be lost through absence from the host state for a period of more than five consecutive years.
Reliable information can be obtained here https://www.lamoncloa.gob.es/lang/en/brexit/howtoprepare/Paginas/190108residence.aspx (scroll down page) and here https://www.gov.uk/guidance/living-in-spain#brexit-what-you-should-do. and here https://www.janetanscombe.com/forms-formalities