What they are, how they are calculated, filing deadlines and common mistakes to avoid.
If you are a freelancer in Spain, modelo 303 is probably the tax form you will file most often. Every quarter you need to calculate the difference between the VAT you charged your clients and the VAT you paid your suppliers, and declare it to the Tax Agency. At the end of the year, you must also file modelo 390 as an annual summary. This guide walks you through how both forms work, when and how to file them, and the most common mistakes to avoid.
Modelo 303 is the quarterly VAT filing submitted by freelancers and businesses to the Spanish Tax Agency (AEAT). It declares output VAT (the VAT you charge your clients) and deductible input VAT (the VAT you pay your suppliers for business-related expenses). The difference is what you pay to the Tax Agency or what the Tax Agency owes you.
All freelancers and professionals registered for VAT-liable activities are required to file modelo 303. Even if you had no activity in a quarter — no invoices issued and no expenses — you must file modelo 303 ticking the no-activity box. The only exception is freelancers who exclusively carry out VAT-exempt activities (such as doctors in healthcare or teachers in official education).
The modelo 303 calculation is conceptually straightforward: output VAT minus deductible input VAT. Output VAT is the VAT you charge your clients when you invoice them. Input VAT is the VAT you pay your suppliers when you purchase goods or hire services for your business. The difference is what you owe the Tax Agency or, if negative, what you can offset or request as a refund.
In practice, modelo 303 breaks down transactions by VAT rate. You must declare separately the transactions at 21%, 10% and 4%, showing the tax base and the VAT amount for each rate. On the input VAT side, you declare the deductible amounts from your supplier invoices. The final result is the total output VAT minus the total deductible input VAT.
Additionally, if a previous quarter in the same fiscal year resulted in a negative balance that you chose to offset (rather than requesting a refund), you can subtract that pending amount. This reduces the amount payable in the current quarter.
Modelo 303 is filed four times a year, always within the first twenty calendar days of the month following the quarter: 1-20 April (first quarter), 1-20 July (second), 1-20 October (third) and 1-30 January of the following year (fourth quarter). The fourth quarter deadline is longer — 30 days instead of 20.
Filing late has consequences. If the result is an amount to pay, the Tax Agency will apply a late filing surcharge that varies depending on the delay — 1% plus an additional 1% for each full month of delay during the first twelve months, and 15% plus late-payment interest from the twelfth month onwards. If the result is to offset or to request a refund, the financial surcharge does not apply, but there may be a formal penalty for late filing.
If in a given quarter the deductible input VAT exceeds the output VAT, the modelo 303 result is negative — meaning the Tax Agency owes you money. This frequently happens when you make significant investments (equipment purchases, renovations), when you have high expenses with low invoicing volume, or when you pay the standard 21% rate on your purchases but sell at reduced rates.
In the first three quarters (April, July and October), if the result is negative you can only offset it against future quarters within the same fiscal year. That is, the balance in your favour accumulates and is automatically subtracted from the positive result of subsequent quarters. Only in the fourth quarter filing (January) can you choose between offsetting or requesting an actual refund. If you request a refund, the Tax Agency has six months to resolve it. If those six months pass without a response, late-payment interest accrues in your favour.
Modelo 390 is the informational filing that summarises all your VAT activity for the fiscal year. It is filed once a year, between 1 and 30 January of the year following the fiscal year being declared. It has no financial result — nothing is paid or collected, it is purely informational.
Modelo 390 compiles the data from the four modelo 303 filings submitted during the year — the total transactions, total output VAT, total deductible input VAT, and the accumulated result. It also includes additional information not present in the 303 filings, such as the volume of operations, the breakdown by IAE tax headings and the prorrata percentage if applicable.
Although it is informational, the Tax Agency uses modelo 390 to verify consistency with the modelo 303 filings. If the figures do not match — for example, if the sum of the four quarters does not agree with the annual summary — it may trigger a formal enquiry. That is why it is important to file the quarterly data correctly from the start.
One of the most common mistakes is including personal expenses as deductible input VAT. Only VAT on invoices directly linked to your professional activity is deductible. If you use a service partly for personal and partly for professional purposes (such as a mobile phone or a vehicle), you can only deduct the proportion corresponding to professional use, and the Tax Agency requires you to be able to justify it.
Another frequent mistake is not keeping complete expense invoices. To deduct input VAT you need the original supplier invoice, and it must meet all the requirements of Article 6 of RD 1619/2012. A simple receipt or a ticket without the issuer's tax ID is not sufficient to justify the deduction.
It is also common to make errors when offsetting negative balances from previous quarters. Offsetting can only be applied within the same fiscal year. If the first quarter resulted in -500 euros and the second in +800 euros, you can subtract those 500 euros. But you cannot carry negative balances from one year to the next — to do that, you would have needed to request a refund in the fourth quarter of the previous year.
CokuApp automatically calculates the output and input VAT for each quarter from your issued invoices and recorded expenses.