This is a minefield for clients contracting in Spain, but pitfalls can be avoided. Ask for the builders damages insurance valid in Spain, this is over and above the Spanish public liability insurance. Any conscientious firm will have this non obligatory insurance.
Ask for proof of the completed previous years tax return in Spain “impuestos de ano anterior” and proof the Spanish tax is paid. Check for embargos.
For real security look for an S.L, a proper registered Spanish company, but still execute the checks from above. For this region the Register Mercantile in Alicante will hold details
Spain Costa Blanca North Moraira, Javea, Denia, Ibiza , Altea, Gandia, Jalon H2R S.L B42610071 web www.h2r.es
Spain Costa Blanca South (Murcia Torrevieja) Hamilton Leon S.L web www.hamilltonleon.com