Many people have contacted the Embassy regarding the need for a certificate proving that they are not Swedish citizens. The Embassy cannot issue such a certificate. The responsible authorities are the Swedish Tax Agency (Skatteverket) and the Swedish Migration Agency (Migrationsverket), which may be able to help.
For more information on how to obtain a certificate (an extract from the population register or other official records) from the Swedish Tax Agency, please see: Information about population registration certificates for foreign government agencies | Skatteverket
Please note: Belgian authorities usually require an extract from the population register (civil registration certificate) issued on a bilingual form.
If you have never been registered at the Swedish Tax Agency (Skatteverket), and do not have a Swedish ID number, please contact Migrationsverket Start page – Swedish Migration Agency