If you ever went through any process in Spain that assigned you a NIE — even years ago, even if you don’t remember the number or lost the document — you can’t request a new one. The NIE is a fixed number assigned once in a lifetime; it never expires or changes. What you need in that case isn’t a NIE — it’s the certificate confirming the one you already have.
The one question that decides which of the two is your case
There’s really only one question: have you ever had a NIE assigned before, even if you don’t remember it or lost the document?
They’re different procedures, with different fees
A new NIE is paid with fee 790-012 for NIE assignment (9,84€). The certificate for a NIE you already have is paid with a different fee under the same 790-012 model, the one for certificates and reports on request (7,31€). Both procedures use the same official EX-15 form — there’s no separate form for the certificate — but the fee and what you’re actually requesting are different.
Why the confusion is so common
This happens mostly to people who lived in Spain some time ago (say, a few months of study or a temporary job) and are now coming back to stay. Because the current situation feels like a completely new process, it’s easy to assume you also need a new NIE. But the number you were given back then is still valid today — you just need to recover the certificate that confirms it.
Verified directly against sede.policia.gob.es, procedure “Asignación de NIE a instancia de interesado”: the same EX-15 form covers both a new NIE request and the certificate for one already assigned, with no separate procedure code for the certificate. Fee 790-012 amounts verified in lib/tasas.ts.