A first Dutch tax year rarely looks like a full one, and plenty of arrivals assume that no letter from the Belastingdienst (the tax office) means nothing to do. Thresholds, the link to toeslagen (income-linked allowances), and the effect of partial-year payroll withholding all decide whether filing is compulsory, optional, or quietly worth doing anyway.
Only if the Belastingdienst (tax office) actually invites you — that letter usually lands in January or February for the previous year, and if it shows up, filing is mandatory. Without an invitation, you still have to file if you'd owe €58 or more, or would get back €19 or more, once you run the numbers — thresholds that are recalculated every year, so treat them as ballpark. You're also on the hook regardless of those thresholds if you claim toeslagen (income-linked benefits) or have savings and investments above roughly €37,395 (or €74,790 combined with a fiscal partner). Where it gets interesting for someone who moved mid-year: even without any of the above, filing voluntarily often pays off. Dutch payroll withholding assumes your monthly salary continues for the full year and applies tax credits accordingly; if you only earned Dutch income for part of the year, your true annual liability usually comes out lower than what got withheld, and the difference comes back as a refund. Worth ten minutes on Mijn Belastingdienst to check, even with no letter in hand.