Ok we have always rented through dollar. I saw the posts about the KLM code for national and signed up for flying blue. Then I just went to check the price of the week we need in June. Is the taxes really included in the price? Just want to make sure I understand the cost.
If you are on the final page of your national rental, with the confirmation number, etc, yes, that will be the final cost, taxes included -- within a few dollars anyway. The rental companies always seems to leave a little wiggle room for extra taxes....but it is never more than a few bucks.
A big CAVET, the code you are using has some decided benefits, and if you can't figure those out by looking at your final confirmation, sorry, I can't help you

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But, in the past few years, most of the time, you can do better if you don't need/want those benefits. For example, right now, Dollar offers city specials (a link that comes up in the middle of your quote when you check prices). Those City Specials have been offering tremendous rates. However, June is so far away, dollar may not be offering those city specials -- yet.
Right now, you are five months out, so the special rate you just got looks good. Try the special rate for your June rental date a few weeks out from your trip, and then try other rates/codes/promos -- National included -- and odds are you can do better.
In other words rates for June are sky-high across the board at probably all firms (Hertz, National,
Avis,
Alamo, etal) right now. As your trip date approaches, those rates will usually drop by a significant percentage, meanwhile, the code you are now getting such great rates with will not drop, or not by much.
So, reserve now with your code if it makes you happy -- but keep checking, all ways and all companies -- unless you absolutely NEED those special benefits (which most do not). The best rates usually come a few days before the rental period (unless they sell-out....oppsies)>