If you're self-employed or run a small business in Spain, form 303 is probably one of the tax filings you'll do most often: a return every quarter, for as long as you're active. Understanding its basic logic saves you nasty surprises and helps you anticipate how much you'll need to pay in (or get back) each quarter.
What form 303 is
Form 303 is the quarterly VAT self-assessment. In it, you declare the VAT you've charged your customers on your sales invoices (output VAT) and the VAT you've paid on your deductible purchases and expenses (input VAT). The difference between the two is, in essence, the return's result.
The basic logic of the calculation
Result = Output VAT (charged to customers) − Input VAT (paid on purchases and expenses)
- If the result is positive, you need to pay that difference to the Tax Agency.
- If the result is negative (you've paid more VAT than you've charged), the amount is carried forward to offset future returns or, in certain cases, you can request a refund.
What expenses let you deduct VAT
Not all VAT paid on your purchases is deductible. For it to be deductible, the expense must be directly related to your business activity and backed by a full invoice (not a simple receipt) in your name. Mixed-use expenses (for example, a vehicle or a phone you also use personally) usually have partial, not full, deduction rules.
Filing deadlines
Form 303 is filed four times a year, on a quarterly basis:
| Quarter | Period | Filing window |
|---|---|---|
| Q1 | January-March | April 1-20 |
| Q2 | April-June | July 1-20 |
| Q3 | July-September | October 1-20 |
| Q4 | October-December | January 1-30 |
The fourth quarter has a slightly longer window and also coincides with the filing of the annual summary (form 390), which compiles the whole year's activity.
A common mistake among self-employed workers who are just starting out
A very common mistake is spending the output VAT as if it were your own income. The VAT you charge on your invoices isn't yours: it's money you collect on behalf of the Tax Agency and will need to pay in on your next quarterly return. Many freelancers who are just starting out get an unpleasant surprise when the quarter comes around and they don't have enough liquidity to cover the payment, precisely because they've already spent that amount as if it were profit.
Quickly calculate the VAT on each invoice
Before filing your form 303, our VAT calculator lets you quickly check the breakdown of taxable base and VAT amount for any invoice or expense, both for adding VAT to a base and for breaking it out of a final amount.