A first Dutch payslip rarely matches the gross (bruto) figure in the offer letter, and then an unexplained extra payment arrives in May. Tax credits, social insurance premiums, the statutory vakantiegeld (holiday allowance) and an optional thirteenth month each account for part of the gap between the two numbers.
Dutch job offers are almost always quoted gross (bruto) because the actual take-home depends on things specific to you — your tax bracket, which credits apply, whether you have the 30% ruling — so bruto is the only number an employer can state cleanly upfront. Your employer withholds income tax and social insurance premiums from every payslip, then subtracts your tax credits (heffingskortingen) automatically before handing you the rest: the algemene heffingskorting (general credit, worth up to €3,115 in 2026 at lower incomes) and the arbeidskorting (employment credit, up to €5,685) are the two biggest, and both shrink as your income rises, which is part of why net pay doesn't scale linearly with gross. The May payment is vakantiegeld — holiday allowance — a legally required minimum of 8% of your gross annual salary, built up over the preceding June-to-June period and paid out as a lump sum, almost always in May, regardless of whether you actually take a holiday with it. If your contract or CAO (collective labor agreement) also includes a "13e maand" (13th month), that's a separate, purely contractual bonus, usually paid at year-end — nothing in Dutch law requires it, so it depends entirely on your sector and employer.