Can I accept a PhD offer and later withdraw from the program before it even starts? Is there an etiquette for that?
I really want to do a PhD but they have put a deadline in accepting and I am currently interviewing with companies. Please advise.
Can I accept a PhD offer and later withdraw from the program before it even starts?
Yes, of course you can. They won't force you to enroll and they won't come after you legally. It's certainly not worth anyone's time. However, it does harm the department's planning because they might not be able to fill your spot. For more discussion, see the comments on this answer.
Is there an etiquette for that?
Yes, the etiquette is to not do that. It's rude and you will burn bridges. A spot that could have been offered to another student may be lost. But if you're quitting to move to industry, you probably don't care anyway.
It's a little snaky, but not the end of the world. If you can give them notice before SEP class starts, they will appreciate that. Maybe they can't fill the slot but there is a chance they can. Also it's better than just not showing up on day 1.
I did that personally and will share the story:
Accepted at one, local, school while interviewing. The timing is difficult to 100% do this in parallel and I was torn. So I explored both options and wanted to have 1 grad school lined up if it was hard to get a job (was during a recession).
A couple years later, I ended up leaving industry and going to a Ph.D. (at a different school). But even the one, I had jerked around before, was still willing to have me, again.
Of the 6 schools, I had earlier been accepted to, 5 of the 6 were willing to take me again 2 years later. It wasn't a big deal and I just portrayed it positively (had been productive for 2 years, but still had a yearning to do more than basic engineering, blabla). Anyhow 5 of the 6 bought that (true, but positive spin) characterization. I guess 1 of the 6 didn't. Also, I did end up finishing the Ph.D. later, doing well, yadayada. IOW I ended up being a good risk.
Note: I'm not justifying this (can anticipate the scolding). Just want to share the practical experiential datum on having actually done it and how it worked out.