Yes you have to pay, the price can depend on the daycare. Accredited and subsidised (‘subventionné/gesubsideerd) daycares will take your income into account if you present a certificate of your income (you can apply for these certificates at Kind&Gezin or ONE). This is the case for all communal daycares, and some private creches. Also, in these daycares you only pay when your child attends (you don’t pay if your child is sick and has a doctor’s note, or for an agreed number of days). These daycares also adjust their rates for large families (3 or more children) and if you have more than 1 child attending at the same time. All childcare costs from daycares that are authorised by ONE or Kind&Gezin are tax-deductible in Belgium.
Daycares that are not accredited are free to set their own tariffs and you will need to pay even when your child is sick/absent for any other reason or during the school holidays. Some offer reduced rates for a second child, but this is not always the case.
Discounts on daycare for children between 0 and 36 months are provided by ONE in two cases: if your income is below the established threshold you receive “basic discount”, or if you have two or more children attending daycare at the same time you receive “increased discount”. To see if you are eligible for this please check: http://www.one.be/parents/accueil-petite-enfance/intervention-accueil/enfant-concerne/
Free preschool/kindergarten begins at 2.5 and most parents take advantage of this.