If students wish to retake the GMAT, there is a policy of waiting a minimum of 30 days between 2 GMAT tests.
The schools will receive all of your scores, from every exam you take. They will take this information into account when evaluating your application.
1st word of advice:
o Schools will not take a negative point of view on your application if you submit two scores as long as there is a significant improvement between them. Schools will notice you made some progress if there is at least a 50-point improvement.
o Before retaking the GMAT, make sure you will be able to improve your score significantly. If you have studied a lot for your first attempt, chances are you will not improve your score the second time. On the other hand, if you took the GMAT with very little practice the first time and you significantly increased your practice in preparation for the second test, you will be more likely to make a big improvement in your score.
2nd word of advice:
Evaluate your score. There are some tools such as the official CAT and PrepMyFuture's mock exams. Some books also provide some self-evaluation grids.
Obtain an estimation of your score before registering for the exam. Even if you can refuse to validate your GMAT at the end of the exam, be sure you have enough training to reach your goal since retaking the GMAT is costly and bad for your application.