Especially at year's end, one of the questions I'm frequently asked is this, “Can I go on leave before I retire?” That's shorthand for “Can I put in my retirement papers and then go on annual leave until I retire?”
It's a question most often posed by former members of the military. That's because terminal leave is one of the benefits available to them when they are separating from the service.
However, if you are a federal civilian employee, it isn't a benefit that's available to you when you retire. That matter was settled by the Comptroller General of the United States as far back as January 1945. In decision B-46683, 24 Comp. Gen 511, he stated that “terminal annual or vacation leave may not be granted immediately prior to separation from the service in any case where it is known in advance that the employee is to be separated from the service.”
Strict as that ruling appears to be, it doesn't mean that you can't take a few days off before you retire. You can, with the approval of your supervisor. However, for your boss to approve it, the amount you request needs to be reasonable. For example, if the date you set for retirement was Friday, December 28, asking to take leave on Friday the 21st, Monday the 24th and even Wednesday the 26th, wouldn't appear to stretch the rule.
While there is no law or regulation that requires you to be at work on the day you retire, it's clear from the Comptroller General's decision that you and your boss should use discretion to avoid the appearance that you are taking terminal leave, which, as noted above, is forbidden.