Since the brain-computer interface (BCI) speller was first proposed by Farwell and Donchin, there have been modifications in the visual aspects of P300 paradigms. Most of the changes are based on the original matrix format such as changes in the number of rows and columns, font size, flash/blank time, and flash order. The improvement in the resulting accuracy and speed of such systems has always been the ultimate goal. In this research paper, we have conducted a set of experiments to determine the errors related to various regions in a region-based P300 BCI paradigm (RB), which is not based on the original matrix format. We have designed RB paradigm in which similar characters are distributed in all the seven regions and user input was recorded using electrodes. The results show that the spelling error related to the center region was highest among the subjects.