Unless you are doing cash jobs and saving it for year end bonuses, then I would just put it on the check. If someone ever came knocking, the employees would be on the hook for paying those taxes. Unless they are stock holders of your company were you could consider this as a distribution. They will still be responsible for some taxes but not all.
As mentioned, discuss with your accountant.
"Just when I thought you couldn't possibly be any dumber, you go and do something like this... and totally redeem yourself!"
