Rate Different on site vs confirmation email?
 

Was checking another reservation and noticed a reservation I have in December is now showing a rate of $1200.
Looked at my confirmation email from July when I booked and it shows a rate of $200.

Will they honor the original rate?
Anything I should do now to make sure it is fixed?

Was the rate booked with a corporate rate code? This sort of thing can happen if the contract between the company and Hertz expires between booking and the rental, and the renegotiated terms are a lot less favorable for that particular rental.

Yes. That was my first horrible thought.

Yergh. If you try to book the reservation now (say through autoslash), what sort of price are you getting? Is the $1200 market rate using publicly available CDP/PC combinations?

If it is a corporate code where the rate deal has changed, then, fundamentally, Hertz isn't wrong. You've got a couple of options, though. You could try to get Hertz customer service to change it now. Alternative, you could do nothing, bring a printout of your confirmation email, and then play dumb at the checkout. If you go that route, definitely have a backup reservation booked.