The aim of the study is to investigate the errors that first grade students have made in their writing of vertical numbers which have just been applied by removing cursive writing. Considering the aim of the study, vertical number writing styles of the first-grade students in primary school were analyzed. The sample of the study consists of 116 students who are studying in the first grade of primary school. The study was defined as a case study. A data collection tool was developed for determining the mistakes that students made while writing the vertical numbers in line with the aim of the research. Through the data collection tool, all numbers from 0 to 9 are given as written statements and it is required to write the numbers in the spaces left under them. The results obtained from the analysis of the data include the existing types of errors that are relevant to the number writing in the students after the first literacy teaching processes. According to the results of the research, writing the numbers oblique, vertical-horizontal-diagonal straight lines are drawn in a curvilinear style, curvilinear and circular lines are distorted, numbers are not aligned in the direction of writing, and some numbers are written in reverse have been seen as the most common errors. In accordance with the types of errors identified in the research, it is thought that the emphasis on dictation studies to increase the awareness of students will decrease these types of errors and their frequency. It is also stated that it is important to diversify the related studies as much as possible, taking into consideration the individual differences of the students.