This case-sensitive code system https://www.ehealth.fgov.be/standards/fhir/etariff/CodeSystem/be-cs-refusal-values defines the following codes:

Code	Display
001	Renewal period not yet expired
002	Maximum number of services already reached over the authorized period (and/or no derogation granted)
003	Service no longer authorized (already reimbursed) for this location (tooth, quadrant, etc.)
004	L600 value reached for authorized period
005	No MC/CTD agreement recorded for the service requested
006	Price consultation is not allowed for this service as it requires the approval of the TTR in accordance with the reimbursement conditions.
007	Consultation of the tariff is not authorized for this service because the tariff depends on other services invoiced at the same time.
008	Prerequisite not met
009	The nomenclature code cannot be attested on this date
010	Service cannot be combined with another service