Carer's allowance

Are you talking about unpaid carer? If so, it’s called aidant proche (mantelzorger in Dutch, I think), and you need to first have your status recognized at your mutuelle. See for example in here: https://www.partenamut.be/fr/services-ma-mutuelle/aidants-proches/statut...
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There aren’t any allowances, but the mutuelles do offer benefits, such as (partial) reimbursement of services paid by titre service, therapy (for carer), cost of respite care, or temp. care at home.
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In addition informal carers with status ´Aidants Proches avec octroi droits sociaux’ can benefit of carers leave, see here: https://www.onem.be/fr/documentation/feuille-info/t164