The ketenregeling, or chain rule, governs how many successive fixed-term contracts an employer may offer before the relationship automatically converts into an indefinite contract. Under the current rule, the fourth consecutive contract or a chain exceeding three years at the same employer becomes an arbeidsovereenkomst voor onbepaalde tijd by operation of law.
The chain breaks only after an interruption of more than six months between contracts. Shorter gaps count towards the total duration and contract number. Employment through associated legal entities or successive employers performing the same work (opvolgend werkgeverschap) is also included, preventing construction-style workarounds.
Sector-specific collective labour agreements may deviate from the default rule. Seasonal work, education sectors, and certain creative industries have tailored limits set out in their CAO. Breaching the ketenregeling does not void the contract; instead, it grants the employee indefinite status with full dismissal protection from the date the legal threshold was crossed.