When applying for the Digital Nomad Visa (Ley 14/2013) outside Spain, you must prove you are a legal resident in the territory covered by that specific Spanish Consulate. For citizens of the country, a national ID or passport suffices. For third-country nationals, this requires a valid residence permit, long-term visa, or local registration certificate (e.g., Green Card in the US, NIE in third countries, or a local ID card).
The document must be issued by the local migration or police authorities. If the document is not in Spanish, a sworn translation (traducción jurada) is mandatory. Generally, apostille is not required for the residency card itself, but it is for supporting civil documents. The permit must be valid at the time of application and usually for at least 3-6 months beyond.
A common mistake is applying with a tourist visa, which most consulates reject as it doesn't constitute 'residence'. Another error is providing an expired ID or a document from a different consular district. If you are already in Spain, this point is replaced by a legal entry stamp or 'declaración de entrada', allowing application directly via UGE-CE.