BNL 1 : visa issued following authorisation by the central authorities.
BNL 2 : visa issued ex officio.
BNL 3 + name of the border point of entry and/or the date of entry: this code will only be
indicated for security reasons in exceptional cases.
BNL 4 : visa issued in the framework of
representation following consultation of the
represented State.
BNL 5 + x days:
the visa holder must report
to the police within "x days".
BNL 8 : visa issued for "medical treatment".
If appropriate, the name of the hospita
l in question can be added to this code.
BNL 9 : NO INSURANCE REQUIRED.
BNL 10 : visa issued for "study purposes".
BNL 11 : visa issued for the
purpose of "family reunification".
BNL 12 : visa issued fo
r "professional purposes".
BNL 13 : visa issued for "business purposes".
BNL 14 : visa issued with a view to "adoption".
BNL 15 : C visas issued to aliens posted to an embassy, consulate, representation or international organisation, and to members of their family, spouse, children and domestic staff living in their household and dependent on them.
BNL 16 : visa issued for "partnership"
BNL 17 : visa issued for "marriage"
BNL18: + name of accompanying parent or guardian: for visas issued to minors who travel accompanied.
BNL19: + name of host: for visas issued to minors who travel unaccompanied.
As you can see, the BNL1/2 just indicate how it was issued.