[jackdaniels]

How many employee's are we talking about? If the number is < 4 or 5, just divide the missing persons bonus between them. This WILL set a precedent saying that when people pick up the slack for others, they get the other persons compensation. They win (by getting a little extra) and you win (since the precedent you are setting is the one you want). Note that this also saves you quite a bit of cash, while still being nice to your employees.

I remember reading Shogun and Toranaga (main character) is considering how to reward one of his underlings. He thinks of a number, then divides it by 2, then divides it by 2 again and gives the result as the reward. He specifically states that it is a lot easier to give a reward than it is to take it back (which is how they may feel next year if you don't make it VERY clear what the extra bonus is for - this year).