The boundary of the village of Kozijak is mentioned in the boundary description of the village Karbinci (do Kozijač’ke megje). The village Karbinci and the land of Kar’ba were subject of dispute between the monks of the Hilandar Monastery and the guards of the emperor. The Serbian Emperor Stefan Uroš IV sent David Mihojević, the kefalija (governor) of Štip, in order to determine the boundaries of the disputed land. The Serbian emperor issued on 8th of June 1355 a chrysobull charter. He confirmed the right of the Hilandar Monastery over the village and the land with the boundaries determined by David Mihojević. The Duke Dmitrь got the village Kozjak as his inherited property from the Serbian Despot Konstantin Dragaš for his loyal service (Iako istini i vьsesrьdьčni surodnikь i brat gospodstva mi vojevoda Dmitrь k věčnomu Tvorьcu i nekonьčavajemu i nemimohodimu i vьsa mira sego ni vь čto že vьměni i vladicě svojemu Hristu priveza se. I sela iže jestь iznašьlь brat gospodstva mi vojevoda Dmitrь, iže mu jestь darovalo gospodstvo mi za jegovo pravověrno porabotanie). He donated the village with all boundaries, rights, vineyard, mills and fruit trees to the Hilandar Monastery. The Serbian Despot Konstantin Dragaš confirmed the endowment of Duke Dmitrь in a charter from 1388/1389 (Selo Kozijakь s metohomь i sь vsěmi megjami i pravinami i sь vinogradomь i sь mlini i sь vokijemь. A se megja sela toga Kozijaka: z gornjega čela poemь ōd Krivoga Dola na Borovi Dol, tako i prěz dolь i prěma grada Kozijaka raspadь do stěne niže glave pod Kučjulatomь, tere na skokь, i ōd tuda prěšьdь dolь megju velikomь glavom i megju malomь, tere na Denkovu nivu, tere više perivolja na Lalulovь studenьcь, tako i niz reku Elьšinicu i do gradišta nad Crьvuljemь i ōd gradišta na dělь izlětši, tako i niz Gabrovь Dolь i ōd Gabrova Dola dolu na rasputije i ōd rasputija koi grěde putь ōd Crьvulje, tere na gradište vse po dělu megju Arьgjuricomь i megju Karьbinьci do prěsdlinje ne došьd ednoga brьdьčca, do trěhь kamenь stanovitihь, do kraine prěsedline i ōd tuda sьvrьnuvь uprěkь na slatinu i ōd tuda prěšьd Kozijašticu na kamenь koi postavismo kon grьma na puti i ōd togai kamena došьd na glavičicu povjeliku z dolnjega kraja grědeki ne došьd Radanьštice i ōd tei glavice uzьbrьdo prěko na srědnju glavu, tako i po hridu megju Kozijakomь i megju Radanōmь na uši Krivi Dolь). The village Kozjak is registered in the Defter for the Sanjak Köstendil in the years 1519, 1550 and 1573.