2026 Tax Calendar: What Changes for the Self-Employed and SMEs with Veri*Factu and the Tax Agency’s Automatic Cross-Checks

The 2026 tax calendar once again demands constant attention to deadlines from the self-employed and SMEs, but this year brings a new factor that’s changing how many businesses operate: the phased rollout of verifiable invoicing systems (Veri*Factu) and the Tax Agency’s tightened automatic cross-checking of data declared across VAT, withholdings, and Corporate or Personal Income Tax. This isn’t just about dates anymore — it’s about keeping your accounting and invoicing in real-time order, because the room to fix things after the fact is shrinking.

What’s in the 2026 calendar

The core structure of recurring obligations stays the same: self-employed workers and SMEs under direct estimation or the general VAT regime still file Form 303 (VAT) quarterly, along with Form 130 or 131 (Personal Income Tax installment payments, depending on the estimation method) and, if they have employees or professionals subject to withholding, Form 111. Owners renting out premises or offices used for business activity must also file Form 115. Once the year closes, the annual summaries follow — Form 390 for VAT, Form 190 for employment withholdings, Form 347 for transactions with third parties above the reporting threshold — and, for companies, Form 200 for Corporate Tax, along with its interim installment payments (Form 202) throughout the year.

The real headline for 2026 is the consolidation of the requirement to use invoicing software that meets the anti-fraud standards known as Veri*Factu: systems that guarantee invoices can’t be altered or deleted once issued, and which, in their real-time mode, send invoice data to the Tax Agency at the moment of billing. The rollout timeline has been adjusted in phases depending on the type of taxpayer, so it’s worth confirming with your advisor or your invoicing software provider exactly when it applies to your business, rather than assuming a generic date. Alongside this, the trend of recent years toward closer scrutiny of self-employed social security contributions under the real-income system (RETA) continues, with the corresponding annual adjustment whenever final earnings don’t match the forecast used to set the contribution base.

At the same time, the Tax Agency keeps reinforcing the automatic alerts and requests it triggers when discrepancies show up between what’s declared on Form 303, 130/131, 190 and, further down the line, personal or corporate income tax returns. These cross-checks no longer depend on an in-person audit — they fire automatically as soon as the figures across forms don’t add up.

What this means for your business

For a self-employed worker or an SME, this translates into a handful of practical decisions. First, check as soon as possible whether your invoicing software (or your accountant’s) already meets Veri*Factu requirements, and don’t leave it until the last quarter — switching invoicing systems mid-year, with clients and suppliers already loaded in, always takes longer than expected. Second, if you contribute to RETA based on real income, it’s worth running a year-end estimate with some lead time — before November — to adjust your contribution base and avoid a final settlement that forces you to repay or claim back large amounts all at once. Third, reconcile VAT charged and VAT paid against what’s actually recorded in your books each quarter before filing Form 303, rather than relying solely on what your invoicing software suggests, since a mismatch between the quarterly 303 and the annual 390 is one of the most common triggers for review.

It’s also a good time to get ahead on Corporate Tax installment payments (Form 202) if your company’s revenue puts you above the threshold that requires filing it, calculating based on actual current-year figures rather than just last year’s results, so you’re not caught off guard in July by a much higher bill than expected. And whatever your legal structure, it pays to review in advance the deductions you’re entitled to — investment, R&D, hiring, digitalization — because many are lost simply from not documenting them in time, not from failing to meet the requirements.

At Zythos Business, this is exactly what we work to prevent: we track the tax calendar business by business, cross-check what’s declared against the real accounting before filing each form, and give clients enough advance notice when it’s time to adjust contributions, installment payments, or bring their invoicing system up to date with current regulations. Knowing that every quarter is reconciled and filed on time is, ultimately, the difference between running your business and letting it run you.