Declaración de obra nueva
Declaration of new building · Obra nueva terminada
The notarial deed, registered at the Land Registry, by which the developer records that a new building exists on the plot.
For a finished building, article 28 of the national Land Act requires a technician's certificate that the works match the project and the occupation authorisation (the first-occupation licence, or a responsible declaration where regional law uses one). Under article 20 of the LOE, it cannot be authorised or registered without proof of the ten-year insurance.
It is the developer's cost on a first sale, and it normally comes before your title deed.
Source: BOE: Real Decreto Legislativo 7/2015, Ley de Suelo y Rehabilitación Urbana (art. 28); BOE: Ley 38/1999 de Ordenación de la Edificación (consolidated)