The end of the quarter is approaching, and with it, one of the most important tax obligations for freelancers and SMEs in Spain: filing the Modelo 303 for the quarterly VAT self-assessment. With the current reference date of September 14, 2026, we are on the verge of the third quarter's deadline. Preparing it correctly is crucial to avoid errors and potential penalties.
1. Gather and Organise Your Invoices
The first step is the most fundamental: having all your accounting up to date. Before filling in any boxes, make sure you have:
* Issued invoices: All invoices you have generated during the quarter (July, August, and September). From these, you will get the output VAT (IVA repercutido), which is the VAT you have charged your clients.
* Expense invoices and receipts: All invoices from suppliers and receipts for deductible expenses related to your business activity. This constitutes the input VAT (IVA soportado), which you can deduct.
Impeccable organisation is the foundation of a surprise-free tax return. Check that each invoice meets formal requirements and that you have correctly categorised each expense.
2. The Impact of VeriFactu on Your Quarterly VAT
Although filing Modelo 303 follows its usual course in 2026, the tax landscape is about to change dramatically with the implementation of VeriFactu invoicing systems. It's vital to understand how it will affect you.
The deadlines are clear: January 1, 2027, for companies and July 1, 2027, for freelancers and micro-enterprises. The good news is that this regulation, far from being an obstacle, will simplify VAT management. A VeriFactu ERP integration or using a VeriFactu gateway for software will allow your invoice data to be communicated to the tax authorities (AEAT) in near real-time.
This means that in the future, the data collection process will be automatic. You won't have to worry about manual processes like importing Excel to VeriFactu or performing complex data migrations like importing from Factusol to VeriFactu or importing from Holded. Compliant software will generate standardised billing records, making it easier to get a much more accurate draft of your Modelo 303. For more details on the deadlines, you can check our guide on when is VeriFactu mandatory?.
3. Filling Out Modelo 303
With your numbers clear, the next step is to transfer them to the form. The main sections are:
* Output VAT (boxes 01-27): Here you declare the VAT you have charged, broken down by tax rate (21%, 10%, 4%).
* Deductible VAT (boxes 28-44): Here you enter the VAT from your business expenses.
* Result (box 71): This is the difference between the output VAT and the deductible VAT. The result can be a payment due, a refund (usually only in the last quarter), or an amount to be carried forward to future quarters.
4. Deadline and Submission
For the third quarter of 2026, the filing deadline is from October 1 to 20, 2026. Remember that submission is mandatory online through the AEAT's Electronic Office.
Anticipating regulatory changes like VeriFactu is the best strategy. If you want to learn more about this system, we recommend reading our complete guide on what VeriFactu is.
Being prepared for the digital future of invoicing is easier with the right tools. Invoicing software like Fakturia.es not only ensures you comply with the Anti-Fraud Law and adapt to VeriFactu without hassle but also automates the preparation of your tax returns like Modelo 303, saving you time and worry.