When you’re dealing with managers and H/R the trick is to have tact.
In this case what I would go to the manager and say this:
“Look I need to take a vacation, so I don’t lose it. I understand it’s not possible right now and I understand the business comes first. Do you think instead of taking my vacation, the company would simply pay me cash instead of the time off?”
The manager will likely say “Ah no” or “Maybe” but it doesn’t matter, whatever the manager says, you say, “You know what, I’ll check with H/R anyway, as I could really use the cash.”
See this option will get you to H/R without undermining the manager. Perhaps H/R doesn’t know this manager is doing this.
The key to getting to H/R is ask a quesiton in such a way the manager won’t know and will have to have you verify it with H/R. Once you go behind a manager’s back or just appear to do this, you’ll have nothing but trouble from that point on.
Usually how employers deal with vacation time is limiting it.
Remember vacation, sick time, even holidays are NOT required in most states, certainly not Illinois.
So an employer can say, you get no more holiday leave till you use what you have. This is legal. Why? Because holiday pay (in IL) is not a right, it’s a benefit.
And you can pick and choose how to apply benefits to your employees as you choose, SO LONG as you are not doing it for discriminitory reasons, such as race, sex, or sexual orientation (not all states or locales)