Modelo 036 / Censos WEB
Modelo 036 is the form you use to register, modify, or cancel your tax obligations with the Agencia Tributaria. It is part of the Censo de Empresarios, Profesionales y Retenedores, which is the official register of taxpayers who carry out economic activities in Spain. If you become an autónomo, open a business, or start any activity that generates tax obligations, this is the form that makes it official.
Modelo 037 no longer exists
Until February 2025, a simplified version called Modelo 037 existed for straightforward registrations. That form was abolished on 3 February 2025. All census registrations and modifications now go through the full Modelo 036, which is completed entirely online via the Censos WEB wizard on the AEAT website. There is no paper version.
What you use Modelo 036 for
Modelo 036 covers three main actions. Alta is the initial registration: you use it when starting a new economic activity, declaring your tax obligations (IRPF, IVA, retenciones), and specifying your activity code (epígrafe IAE). Modificación is used when something changes: a new address, a change in activity, adding IVA obligations, or registering in the ROI for intra EU transactions. Baja is used when you cease your activity entirely.
The Censos WEB wizard
The Censos WEB wizard at the AEAT sede electrónica guides you through the form in a series of tabs. Tabs 1 through 3 cover personal data, address, and representative details. Tab 4 is where you declare your economic activity and IAE code. Tabs 5 through 9 only appear after you save an activity in tab 4. These cover IRPF obligations, IVA regime, withholding obligations, intra EU operations (ROI, tab 7), and digital services to EU consumers (tab 9). The Sign and send button only becomes active after completing all applicable tabs, but clicking it does submit the form.
You need a Certificado Digital to access the Censos WEB wizard. Cláve access is limited for this form.
Common mistakes
Choosing the wrong IAE code is the most frequent error. The code determines which tax obligations the system assigns to you. Changing it later requires a modification filing. Another common mistake is confusing ROI registration (tab 7, for B2B EU clients with VAT numbers) with the digital services regime (tab 9, for B2C EU consumers). These serve different purposes and trigger different quarterly obligations.
