Expired or lost passports – Belgium
If you are a Belgian national, you should have a valid passport or ID card to enter/leave Belgium. However, nlfr allows you to (re)enter Belgium with an expired passport, if you can provide valid proof of your identity and nationality.
Nationals of other EU countries are advised to have a valid travel document (passport or ID card) to be able (re)enter Belgium without any problems.
In any case, you should check with the consular authorities before travelling.