Spanish Freelancer Tax Forms Explained: Modelos 036, 037, 111, 130, 303, and 390
The first Spain-specific control is not a quarterly return. It is getting the setup lane right. AEAT's [census page for empresarios, profesionales y retenedores](https://sede.agenciatributaria.gob.es/Sede/censos-nif-domicilio-fiscal/tramites-censales-relacionados-empresarios-profesionales-retenedores.html) and the [Modelo 036 procedure page](https://sede.agenciatributaria.gob.es/Sede/procedimientoini/G322.shtml) are the cleanest starting points for tax registration, while Importass says you must request [alta en trabajo autónomo](https://portal.seg-social.gob.es/wps/portal/importass/importass/Categorias/Altas%2C+bajas+y+modificaciones/Altas+y+afiliacion+de+trabajadores/Alta_trabajo_autonomo) before starting the activity and can do it up to 60 days early.