Let talk about the confusion many people have and correctly so, with all the misinformation going about!
Please note This is AFTER you have had the NLV approval and the EU residence Status as without either of these you are not legally allowed to be here over the 183 days without them or other approved permission
To Start with let's discuss the "183 days"
Individuals become officially resident in Spain for tax purposes, here it is called fiscal residence and if they live more than 183 days of the calendar year on Spanish territory, this is when the information becomes confusing as a lot of people mention being here on holiday previous to moving full time.
Now from a tax perspective this is based on where their principal centre of activity or physical base of their economic interests lie.
A presumption of residence arises if an individual's family lives in Spain, thus becoming the Fiscal, if however the person's previous interest lie in another country, lets use the UK for example and they are paying their taxes in this country on the visit to Spain then that is where their tax is due not Spain and does not need to be accounted for, UNLESS any work is or has been carried out in Spain on the time spent previously to gaining the resident status, having said this it is always best to discuss YOUR individual circumstances.
You should also be aware that ANY homeowner in Spain is required to file the 210, as a non resident, and while this is or has been filled you cannot be both fiscal and non fiscal at the same time as the Spanish Tax year runs from the January 1st to December 31st, again being only fiscal after 183 days, under normal circumstances. The Uk along with 90 other countries have the use of the Double Tax agreement
In addition to the question am i resident ?
Here is the criteria
A person will be resident in the country in which their permanent residence is located.
If they happen to have permanent residences in both countries, they will be considered resident in the country in which they have the strongest personal and financial ties (centre of vital interests).
Failing this, they will be resident in the country in which they mainly reside.
If they split their time equally between both countries or do not live in either, they will be considered resident in the country of which they are a national.
If they are a national of both countries, or of neither, the responsible authorities of each country will decide the individual’s country of residence by mutual agreement.
Once you have the TIE card for NON EU or have obtained the Green Card for EU nationals and unless you can prove otherwise your status in Spain is Resident, this does mean then that you are liable for the Tax and the other responsibilities in Spain over the 183 days of residing here, from this point onwards unless the above applies.
Spain has a various amount of Visas, not just what you are aware of but for this question and the most sought after visas, such as the NLV and EU Residencia Including the WA, the first 5 years are Temporary, the NLV having to have renewals at various stages, then you can apply for Permanent Status after this.
Remember this is only in relation to the above visa on the post, others i can advise on if required.
Bear in mind for the renewals of the NLV even if you do not need to do a Tax return and of course you are not at a disadvantage of doing so, it's advisable to do one in order to show at renewal you are serious of your status in Spain.
This is your new home, you have dreamt it, now live it and respect it.
So please ask an expert for advice on this and not the Facebook "experts" who know how to say "183 days" but not Why they are saying it!