In Belgium, church and the state are legally separated, so you want find any information about religion in birth, marriages and death records of civil registers. To a large extent, Jewish genealogical research in Belgium since 1830 is not different from research for the rest of the population; information about Jewish records you will find only through additional sources.
The website of the State Archives [https://search.arch.be/en] can inform you how to find your way in the archival system of Belgium.
Belgium has four basic civil resources for genealogical research: State Archives, Provincial Archives, City Archives and communal civil registers.
Birth, marriages and death records from 1811 until 1920 can be viewed on microfilm at the State Archives.
Each of the nine Belgian provinces has a reading room in their provincial premises. These reading rooms are generally open weekdays between 8h30 to noon and from 13h till 16h30.
Documents about records from civil registers microfilmed by the Mormons (the Church of Jesus Christ of Latter-Day Saints) can eventually be ordered through their Family History Centers worldwide.
The original documents are kept in the municipalities where access is granted on a case-by-case, general depending on the physical condition of the documents or on local communal customs. In some cases original documents have been microfilmed and are available, but in other cases they are not.
Files less than 100 years old are kept in recording offices of the Civil Registry Office. Those offices of the Civil Registrar keep the registers of birth and civil marriages as well as the registers of death of all residents in Belgium, both for Belgian citizens and foreigners.
Even in the case a Belgian Jew is buried in the Netherlands, a death certificate will be deposited in the place of residence. All death must be certified by a physician who attests the cause of death. Death records do not record where the deceased was buried or cremated. If the deceased died elsewhere than his regular residence, the death certificate will be transferred to the place of residence.
To know where a Jew was buried, you have to inquire with the local Jewish community where the deceased had his residency.
You have also a private Jewish burial society: the Frechie Stichting (the Frechie Burial Foundation), a private Jewish burial society that mainly buries Dutch-speaking Jews who are mostly originating from the Netherlands and live in and around Antwerp.
Federal law on the protection of personal data prohibits research of files less than 100 years old, except in two cases: when a person wishes to have access on his own personal data in case this information is necessary to prove a progeny or also for some other legal reason. In this case you can ask the permission to consult personal data by sending a request to the Court of First Instance which has judicial competence for the respectively place. Costs and expenses for administrative steps will be borne by the person who makes the request.