In the coming weeks, many of you will find a new kind of “invoice” on the mat: the Belastingdienst is sending out the voorlopige aanslag for 2026. This isn’t noise. It lands right where small businesses feel things first: cash flow. If you treat it like background admin, it can quietly squeeze your liquidity, push other invoices down the line, and create stress you didn’t need, especially if you’re already juggling VAT returns, suppliers, and a client who pays “next week” every week.

A voorlopige aanslag is simply a provisional tax assessment: an estimate of what you’ll owe for 2026, paid in advance. You can pay it in one go or in installments, with the final due date on 31 December 2026. Think of it as the tax office saying: “Based on what we currently believe your year will look like, we’d like you to start paying now, so it doesn’t all hit at once later.” That can be helpful, until the estimate doesn’t match your real year.

So where does that estimate come from? The Belastingdienst bases it on what it already knows: your most recent income tax return, earlier provisional assessments, reported results from previous years, and any changes you’ve communicated (for example, a different expected profit). In plain language: they look at your track record and assume the coming year will resemble it. If your business is stable, the estimate is often close enough. If your turnover swings, if you’ve just started, if you’ve taken on staff, raised prices, paused work, or invested heavily, the estimate can be off, sometimes by a little, sometimes by a lot.

This is where the real risk shows up for micro-entrepreneurs: not in the concept, but in the timing. One strong year can lead to a higher provisional assessment the next year, while your current year might be quieter. I see it often: a freelancer had a good 2025, then a key client pauses projects in early 2026. The provisional instalments keep going, because the Belastingdienst doesn’t automatically “feel” your slowdown. Meanwhile, your own invoices are coming in later, your buffer thins, and you start making choices you shouldn’t have to, like postponing a supplier payment or skipping that sensible quarterly reserve.

The calm fix is to treat the voorlopige aanslag like any other contract-based obligation: check whether the assumptions still match reality. If you expect 2026 to be materially different, higher profit, lower profit, more deductions, fewer hours, make sure your expectation is reflected, so you’re not paying too much too early or too little and facing a nasty catch-up later. Too high means unnecessary pressure on your bank balance; too low means a bigger bill at the end and a hit to trust in your own planning. Neither is dramatic, but both are avoidable with a small, timely adjustment.

There’s no need for alarmism here. The provisional assessment is not punishment; it’s a payment schedule built on imperfect information. Your job is not to predict the future perfectly, it’s to keep your business steady while the future unfolds. If you do one thing, do this: connect that letter to your real numbers, not your hopes. A modest buffer, a realistic estimate, and a monthly look at profit versus last year will usually keep you in control. In a small business, calm is a strategy, and good tax planning is often just good cash-flow hygiene.