Ideally, you shouldn’t be taking a break from work to write the GMAT. Having said that, some students do take breaks, and it doesn’t affect their applications negatively.
Ensure that you start working immediately upon completion of the GMAT.
Things you need to be aware of:
1. Sometimes people are not really able to improve upon their score inspite of taking a break. In such a scenario, the break itself is wasted.
2. The prep period is not very well defined. Students usually start with a 3-month prep plan, and it is quite common for them to extend this indefinitely. If you are not good about sticking to your plan, you may end up taking a much longer break than you had originally intended.
3. Consider also the possibility that you may not find a suitable job so that you can get back to the workforce just as you finish your GMAT. This has a way of affecting the application as well.
4. Finally, consider the fact that all students who are going through the same process as you, are facing the same difficulties with regards to juggling work and GMATprep. If you have to take a break in order to focus on one of these two aspects, you may be indicating to the admissions committee that you are not able to manage your time as efficiently as some of the others.
Hope this helps!