This special expats tax regime results in an important tax incentive for those highly skilled workers who come to Spain for work reasons.
Above all, it consists of taxing by a fixed percentage of 24% up to 600,000 euros. In addition, it does not happen as with residents and you are only taxed in Spain for income earned in Spain.
As a result, this system is not interesting to everyone since for annual rents of less than 50,000 euros it will be more advantageous to pay taxes as a normal resident. But from there you should start to assess the personal situation to assess what would be the best option.
Importantly, it is an option that must be requested when arriving in Spain (6 months term) because otherwise the option is lost (and you will no longer be eligible for its application again until you have spent 5 years being non-resident). But if you choose this option you could consider in a later year you stop to applying it because for example you have had several children and when making the joint declaration it would be more beneficial to tax as a resident. It should also be noted that the deductions and reductions that can be applied to persons with this special taxation regime are very limited (although there is recent case-law in this regard and it is something that has changed in recent years).
In some cases it is very easy to determine the interest in its implementation and carry out the procedures to benefit from the regime but it is always advisable to have a professional review also because there are certain aspects that must be carefully reviewed such as those related to the employment relationship.
Feel free to contact for a study and assessment adapted to your personal situation.