Whether you want or need advance notice of resignations depends on the nature of your business. If you are in an industry where people commonly come and go, and where it's relatively easy to find good replacements, you may not care about advance notice. If you want exiting employees to train their own replacements, a two-week notice period may be a reasonable request.
Lame duck employees. In some cases, you may decide that you don't want a "lame duck" employee around. If you have established a notice policy, fairness requires that you pay the person for the remainder of the notice period, if you decide that you don't want him or her to work out the entire period.
Establishing a notice policy. How do you establish a notice policy? Just place it in the list of work rules that you give to incoming employees.
The following could be placed in your list of work rules:
We hope that you will never find it necessary to resign. However, if you do, we ask that you give at least two weeks' notice. Proper notice allows us to prepare your final paycheck and separation papers, and preserves your record as a responsible and cooperative employee. In some cases, we may choose to pay your two weeks' salary rather than require you to work the two weeks. If you don't give the required notice, you may become ineligible to be rehired in the future.
Don't threaten to withhold benefits or pay. Can you threaten to withhold benefits or pay if a resignation procedure is not followed? Probably not most states have laws requiring that employees be paid whatever they have earned, and paid on time. Penalties have been imposed even where there were only minor delays in paying the last check.