The social security number is how Spain's social security system identifies you. You need it to be hired, to register as self-employed, to access public healthcare and to claim any benefit.
You request it once. It stays with you for life, through every job and every change of status.
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It is an identifier, not a card and not a permit.
Without it, no employer can register you, you cannot register as self-employed, you cannot be enrolled in the regional health system, and you cannot receive a pension or benefit.
It is free, and you only ever apply once.
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This is where most newcomers lose a week, because there are four names and two of them are the same thing.
NUSS and NAF are the same number. Social security calls it both the social security number (NUSS) and the affiliation number (NAF). If someone asks for one and you hold the other, you already have it.
The NIE is your foreigner identity number, issued by the police. It identifies you as a foreign national.
The NIF is your tax number, used by the tax agency. For a foreigner it is usually the NIE.
One identifies you to social security, one to the police, one to the tax agency. Holding one does not give you the others.
If you do not have a NIE yet, that comes first: how to get an NIE number.
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Check before applying. Applying when you already hold a number produces a rejection and lost days.
You have one if you have ever worked in Spain, even briefly and even years ago. It appears on your working life report, on any old payslip, and on the health card issued through employment.
If you cannot find any of those, you can check it on the Import@ss portal using Cl@ve, electronic ID or a digital certificate.
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This is the fast route. With Cl@ve, electronic DNI or a digital certificate, you open the social security number request on Import@ss and fill in your details.
You will need:
Because you identified yourself electronically, social security already knows who you are, so there is no separate identity check to wait for.
If you do not have a digital certificate yet and expect to deal with Spanish administration more than once, it is worth getting first.
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This is the situation most newcomers are actually in, because getting Cl@ve usually requires having done something first.
You still apply online, but you prove your identity a different way:
The difference is timing. Without electronic identification, the TesorerĂa General has to verify who you are before resolving, so the request sits pending rather than being processed straight away.
Make the selfie count. Your face and the front of the document both have to be visible and readable in the same photo.
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A parent or legal guardian applies, and the paperwork is different:
This is the one case where the TA.1 form always appears. For adults applying online, the web form replaces it.
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Two different things, and confusing them costs people real money.
The number identifies you. Registration (the alta) is what gives you cover and creates the obligation to pay contributions.
If you are being hired, your employer files the alta. If you are going to work for yourself, you file it, and that is the next step.
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The full process is in how to register as autĂłnomo with social security.
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Applying when you already have a number. The most common one. Check first.
A selfie that fails verification. Blurred, glare on the document, or the document held at an angle.
Giving a phone or email you do not check. Requests for more information go there.
Assuming the number lets you start working. It does not. The alta does.
Starting a self-employed registration without it. The filing fails, and people often only notice when no contribution is charged.
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Nothing. It is free.
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Yes. Social security uses both names for the same number.
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Yes, online, by uploading photos of both sides of your document and a selfie holding it. It takes longer because your identity has to be verified first.
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You need a valid identity document, which for a foreign national in Spain is normally the NIE. They are separate procedures at separate bodies.
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No. Contributions start with the alta, which is a later and separate step.
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No. It is for life. If you do not remember it, look it up rather than applying again.
Related: How to get an NIE number / How to register as autĂłnomo with social security / Social security for autĂłnomos
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