Starting from the historical development of South Slavic languages with an emphasis on Croatian, Bulgarian and Slovenian, this paper presents the beginning of Slavic literacy, the graphic systems of these languages as well as the development of spelling and the principles on which they are based. Graphic systems of the three languages are presented, with certain differences, such as the use of different letters. The development of spelling manuals over the years in all three languages has been influenced by various political developments, and linguists have fought individually or in groups for quality spelling. Language is realized through speech and writing, and each language contains its own language system that must have certain norms. There is a spelling norm that is realized by writing, and it is closely related to speech. For correct writing, therefore, the spelling principles that make up spelling must be respected. In addition to the above, this paper presents certain spelling solutions on which the spellings of the Croatian, Bulgarian and Slovene languages are based. These solutions start from the fact that the Croatian orthography is phonological with morphological elements, and Slovenian and Bulgarian morphological. The final part of the paper presents the rules for writing foreign names in all three languages. The observed similarities and differences between the spellings of these languages in general, as well as the writing of foreign names,. are highlighted in the last chapter.