For anyone living in Spain or with fiscal interests there, should consider bookmarking it for future reference. Besides explaining what all of the most commonly used Spanish tax forms (modelos) are for, it also has links to their downloads.
The first one covered in the guide is the Modelo 30 which is the most commonly used of all the forms, for private individuals - as opposed to businesses - any way. As the guide says this is the form you use to sign up for Spanish tax in the first place. If you become liable to tax in Spain or think you may be due a tax refund (see Getting a Spanish tax refund) then it is necessary to register using this form. The same form is used if you become liable to Spanish NON resident income tax, which all foreign owners of Spanish property or assets probably are (unless they are residents).
A lot of people expect that if they are liable to tax in Spain they will find out soon enough i.e. they will be sent a tax return or demand and take action accordingly. Others think that by obtaining their NIE number or residency certificate, that identifies them to the Spanish tax authorities. Neither is true - the modelo 30 is the only way to register for Spanish tax.
Luckily it is an easy form. We process these for clients but you could do it yourself easily enough. Go to your local Agencia Tributaria and you will see a desk somewhere near the entrance where they hand out tax forms. Ask for a modelo 30 and fill it in there are then. It is relatively untaxing information like name and passport number. One tip is that if you are registering as a couple, you use one form and put a cross in both boxes 101 and 102 on section 1 (the other half is the "conyuge') . Then you fill in one spouse's personal data in section 2 and the other in section 3. Both sign at the end. Simples.
Note that the modelo 30 is also used to modify any aspect of your tax status and it is an offence not to do so. Things that would trigger a modification:
- change of adress (Spanish)
- change of residency status e.g. becoming a resident after previously paying non res taxes
- end of residency e.g. you are leaving Spain and are no longer liable for tax
- change of marital status