2026 Tax Calendar: The Deadlines No Freelancer or Small Business Should Miss

Every year brings the same challenge for freelancers and small businesses: keeping track of tax deadlines. The 2026 calendar follows its usual structure — quarterly VAT and income tax payments, annual summaries, Corporate Tax instalments — but it’s worth paying close attention, because deadlines don’t bend for anyone. Filing a return even one day late, whether by mistake or oversight, automatically triggers surcharges from the tax authority, and they grow the longer the delay goes unresolved.

The quarterly routine remains the backbone for most businesses: VAT returns (Modelo 303) and, where applicable, income tax instalments (Modelo 130 or 131) are due within the first twenty calendar days of the month following the end of each quarter — except for the last quarter of the year, which is filed in January together with the annual summaries (VAT in Modelo 390, withholdings in Modelo 190, third-party transactions in Modelo 347). Businesses with employees or rental payments subject to withholding also file Modelo 111 and 115 on the same quarterly schedule. Companies, meanwhile, need to keep an eye on Corporate Tax instalments (Modelo 202) in April, October and December, followed by the annual Corporate Tax return itself a few weeks later. Running alongside all of this is the annual income tax campaign each spring, which means reviewing draft returns, regional deductions and any outstanding adjustments from the previous year.

What this means for your business

Beyond memorising dates, what matters is the concrete decisions this calendar should drive. First, cash flow: freelancers and small businesses need to set aside VAT charged and withholdings deducted systematically, month by month, rather than treating them as available cash. This is the most common mistake — and the one that causes the most penalties — when the quarter arrives and there’s no liquidity to pay over money that was never really the business’s own, but the tax office’s or the employees’. Second, staying ahead on paperwork: invoices, deductible expenses and supporting documents should be in order before the filing window opens, not during it, since scrambling through the books under time pressure is the fastest route to errors on the return — and, later, to formal requests for information. Third, the growing digitisation of dealings with the tax authority — electronic notifications, mandatory online filing, and the gradual move towards mandatory e-invoicing between businesses — makes it worth reviewing the invoicing tools in use, since systems that don’t leave a clear trail for every transaction are an increasingly poor fit for what the authorities will require. And fourth, freelancers who pay social security contributions based on net income need to keep adjusting their income forecasts throughout the year, since a significant gap between estimated and actual earnings can lead to a contribution adjustment — for or against them — when the annual reconciliation comes through.

How to avoid surprises and penalties

The best defence against this calendar isn’t memorising it — it’s automating it: block out each quarter’s closing dates well in advance to allow time to gather documentation, check before filing (not after) that figures and totals match the books, and never leave a return until the last day of the deadline, since any last-minute technical hiccup — whether on the tax authority’s own portal or in your accounting software — can turn a simple oversight into a late filing, surcharge included. It’s also worth periodically checking that all applicable deductions and allowances are still being claimed correctly, since many go unused simply out of not knowing they apply, not because the business doesn’t qualify.

At Zythos Business, we turn this calendar into something our clients don’t have to watch themselves: we track every deadline, prepare and file each return with the accounts already verified, and flag anything that needs a business decision with plenty of notice — so freelancers and small businesses can spend their time on what actually grows the business, not on chasing tax office dates.