This was announced by the church in a recent annual report.
Many cited a "revulsion at sexual abuse" within the church and a "culture of silence" as the reason.
The Flanders region and the archdiocese of Mechelen-Brussels recorded 98 per cent of applications for removal from the baptismal register. It is not possible to formally leave the church in Belgium.
According to the figures, around 1,200 people have applied to be removed from the baptismal register each year so far; only in 2021 did this figure exceed 5,000. No official reasons need to be given for this step.
According to the church, last year's broadcast of the documentary "Forgotten by God" led to the significant increase.
The programme, which was broadcast on the Flemish public broadcaster VRT, featured interviews with around 20 victims of sexual abuse, mainly older men who had been abused as teenagers in Catholic institutions.
Debate about abuse during the Pope's visit
Abuse was also a central topic during Pope Francis' visit in September. At the Vatican embassy, he met 17 victims of sexualised violence by Belgian clergy. The meeting lasted more than two hours.
Afterwards, the head of the Church called the abuse of minors a disgrace. "We must recognise this shame, ask for forgiveness and solve the problem."
The Belgian parliament had previously decided to set up a new committee of enquiry to investigate abuse in the church.
Belgium could also see more resignations than usual this year.
After the Pope's trip , 524 Belgians announced in an open letter that they would be "de-baptised".
They were protesting against statements made by Francis during his visit to Belgium, in which he described an earlier law liberalising abortion as "murderous".