The retention for IRPF (income tax) differs depending upon whether an individual is fiscally resident or not. For this reason your future employer has indicated that you are not tax resident and the retention will be higher at 24%.
When one then comes to prepare and file an annual tax return these monies are taken into account and any over-payment is repaid. Alternatively, if your actual tax exceeds that retained you will pay the difference.
Over the course of time this retention will reduce when you become tax resident.
G Mor?n
CB Legal & Fiscal
info@legalandfiscal.com