službeno

1. on business
   Sledeće nedelje idem službeno u Novi Sad. — Next week I'm going to Novi Sad on business.
2. officially
   Vest još nije službeno potvrđena. — The news hasn't been officially confirmed yet.
   Obratio se službeno direktoru škole. — He formally addressed the school principal.

For "officially" Serbian more often uses zvanično.