According to the law, your arrival in Spain must be a consequence of the new employment contract or relocation from your current employer. Although it is normal that you arrive in Spain sometime before the start of your contract (to find housing and arrange schooling for children, among others), Spanish tax Authorities can dig deeper and question your arrival date and when did you get the job offer. In case your arrival in Spain was before the start of the job negotiations or the job offer, they could deny the Special Expatriate Tax Regime.