promena osnova rada

1. (of a work permit) change of the basis for a foreigner's employment
   Predala sam zahtev za promenu osnova rada. — I submitted an application for a change of the basis of employment.
   Otvorio sam preduzetničku radnju, pa prijavljujem promenu osnova rada. — I registered as a sole trader, so I'm reporting a change of the basis of employment.

Osnov rada means the legal ground for working (employment with a company, self-employment, etc.), not the workplace itself.