Sometimes an examinee may not feel satisfied with his/ her performance in the exam. In that case he/she may go for retaking TOEFL IBT.
However, ETS do print your previous test results on your new Score report sheet.
It should be kept in mind that the examinee should be completely sure, that he/ she want to reappear for TOEFL. It means that if one has got a good score as per demand of universities but that good score is less than the personal expectations of the candidate, it will be better not to reappear, as the main motive of giving the test has been fulfilled.