Who files this?
Freelancers subject to VAT. If all your transactions are exempt or outside the scope of VAT (e.g. healthcare, education, or services to clients outside Spain without reverse charge), you may not need this.
What does it declare?
Output VAT from your sales minus deductible input VAT from your expenses. If positive, you pay Hacienda the difference. If negative, it carries forward to next quarters or you can request a refund in Q4.
When is it due?
Deadlines: 1–20 April (Q1), July (Q2), October (Q3), 1–30 January next year (Q4).
In Autónomo Simple
Autónomo Simple calculates Modelo 303 automatically. Output VAT comes from your invoices and input VAT from your expenses with the deductible percentage you configured.