Once upon a time, giving advance notice upon resigning from a job (usually two weeks) was automatic. Unquestioned. Failure to do so would be considered immature, irresponsible and unethical.

But you know what? Nearly all states in the U.S. now adhere to the doctrine of “at-will employment.” This means that both you and your employer are free to end an employment relationship at any time, with no warning, and for no stated reason.

What’s more, there are a few cases where you might consider doing just that.

Naturally, if your employer is requiring you to work under unsafe conditions or engage in unethical or illegal behavior then you need not — indeed, you should not — delay your departure. The same goes for situations where the employer has abused you, sexually harassed you or failed to pay you.

If you’ve observed that the moment other employees resign they are quickly walked out the door and not allowed to return, and you have good reason to assume the same would happen to you, it would probably be wise to dispense with the notice-giving. Two weeks’ notice should not cost you two weeks’ pay.

Finally, if you’re facing a serious personal emergency that requires your full and immediate attention, advance warning may simply be out of the question. Being sincerely apologetic and as forthright as you can be will help most employers to understand, even sympathize.

No matter why or how you leave a job, don’t forget to first consult your company handbook or contract, if you have one. You may have agreed to a clause stipulating a set amount of notice upon resignation. Also smart to do in advance is to remove personal items from your workspace and check to see if you still have vacation or sick days coming to you. Depending on your employer, it might be best to take those days while you still can. You never know.

Of course, it’s always good to end any job on the best possible terms. Keep in mind that you are leaving not only your boss and company but your co-workers, customers, clients or patients. If you can, and you’re sure it won’t come back to bite you, consider tendering that traditional two-weeks’ (or more!) notice. It’s a small world, and you never know when you and your former employer will cross paths again.