The loonheffingsnummer is the wage-tax registration number that the Belastingdienst issues to an employer as the unique identifier for payroll reporting. Without this number, a business cannot lawfully run a Dutch payroll, deduct loonheffing from gross pay, or file the monthly aangifte loonheffingen.
The number is derived from the employer's fiscal number and suffixed with a three-character subnumber such as L01. Each subnumber represents a separate wage-tax declaration unit, allowing group companies or multiple business lines to separate their payroll reporting while staying linked to one legal entity.
A new employer applies for a loonheffingsnummer through the Belastingdienst online form or via the first employment registration, typically after the company is entered in the KVK handelsregister. Foreign employers with Dutch payroll obligations receive a loonheffingsnummer through the Belastingdienst Buitenland office in Heerlen.