From our agents in pet friendly Serbia at Move One:
Effective from middle of August, and following the legislation issued on December 23, 2008, residence permit stamps in Serbia have been replaced with residence permit stickers. Information included on the stickers will hold the same amount of information as the stamps previously used by the authorities. Foreign nationals who still hold residence permits with the old type of stamp are not required to update their documents.
New sticker will be issued upon application for a residence permit extension. The new Law On Foreigners has been also published in the 'Slubeni glasnik RSޢ No. 97/08 of 27 October 2008, and has been applied from 1 July 2008. Based on this legislation, foreign nationals entering Serbia on a tourist or business status can stay in the country for maximum of 90 days within a 180 days period. In the past a foreign national could step across border before their ninetieth day and re-enter the very same day to be granted another 90 days of stay, which was a loophole in Serbian immigration law.