Visa
Third-country nationals require a national visa
when they are going to stay in Spain for more than
90 days (in any 180-day period) for the purposes of
work, study or establishing their residence. They
also need a national visa when moving to Spain to
work for a period of under 90 days.
Citizens of the European Union or of the States of
the European Economic Area or Switzerland do not
need a visa to establish their residence in Spain or
for long-term studies or to work. However, once in
Spain, they must be entered on the Register for
Citizens of the Union. Family members accompanying
them, and who benefit from the right to free
movement, must apply for a residence permit in
Spain. If they need a stay visa because of their
nationality, they must obtain a visa for family
members of a citizen of the Union (see section
"Visas for family members of a citizen of the
Union").
The national visa allows the holder to travel to
Spain and to transit through and move around the
territory of any Schengen State for a maximum of 90
days. However, it does not automatically entitle
them to enter the Schengen area. The border
authorities can refuse entry if not all entry
requirements are met (See section "Conditions for
entry into Spain").
More Spainish Visa information, please check here: https://www.exteriores.gob.es/Embajadas/seul/en/ServiciosConsulares/Paginas/Consular/Visados-nacionales-Informacion-general.aspx
ICAME letter of Invitation
A Letter of Invitation is a proof that your paper submission and registration application are accepted by the conference committees board. It perhaps could help with your visa application. However, it does not guarantee you a visa.