Here's a breakdown:
* Early Stages: If you accept an offer and then quickly realize it's not the right fit (within a day or two), contacting the admissions committee immediately to explain the situation and politely withdraw your acceptance is generally acceptable. The quicker you do this, the better.
* Later Stages: If you accept and then later (weeks or months) decide to decline, it reflects poorly on you. The program has likely already begun planning for your enrollment, possibly offering your spot to others on the waitlist. This can cause disruption and inconvenience. You might damage your reputation with that specific program, and possibly even with other programs if word gets around.
* Consequences: The consequences could range from:
* No negative consequences (if you withdraw very early).
* A damaged relationship with the program. They might be less likely to consider you for future opportunities.
* A formal record of your withdrawn application in their system. This might affect future applications.
* A loss of financial aid or funding if you've already been granted any. You might be required to return any funds received.
Before accepting an offer: It's crucial to thoroughly research the program, faculty, and funding opportunities before committing. Consider visiting the campus if possible, and speaking to current students to get a better feel for the environment. If you have any doubts, it's better to delay accepting the offer until you are certain.
In short, while technically possible, declining a graduate school offer after accepting it is best avoided. Honesty and prompt communication are key if you need to change your mind.