WAB premium differentiation is the employer-paid unemployment insurance premium structure introduced on 1 January 2020 by the Wet arbeidsmarkt in balans (WAB). Employers pay a low WW-Awf rate for workers with a written permanent contract for a fixed number of hours, and a substantially higher rate for all other contracts, including most agency and on-call work.
The low rate applies only when the contract is in writing, indefinite in duration, and not an on-call arrangement. If a worker exceeds 30 per cent more hours than contracted in a year, the low rate is retroactively corrected to the high rate, except for contracts of 35 hours or more per week.
For hirers and agencies, the differential creates a strong cost incentive to convert long-running flexible roles into permanent employment, and it is a key input when pricing staffing, payrolling, and employer-of-record services.