This is a charge that is in Hertz's terms for Ireland. From
https://www.hertz.ie/rentacar/reservation/reviewmodifycancel/templates/rentalTerms.jsp?KEYWORD=CDW&EOAG=WATE61
Originally Posted by Hertz
If you decide not to purchase CDW, you may be required to provide a security deposit of € 5,000.00 at the start of the rental using your credit card. If this amount is not available on your credit card, you will have to purchase Collision Damage Waiver (CDW) and Theft Protection (TP), or you may be refused a vehicle.
If you book a basic rate and do not take the cover products available at time of rental you understand that you are financially liable for the full value of the vehicle and related costs.
Reliance on an external policy or eligible credit card for coverage will require documentation that this cover is applicable for the Republic of Ireland. As these products are limited, to protect against shortfall in cover a €7 per day Supplementary Liability Waiver (SLW) charge will apply.
Given that this is a documented charge, I cannot see much chance of a dispute having any success ; the security deposit is also a listed item
This doesn't seem unique to Hertz ; EUR5000 deposit and a EUR30 fee applies with Avis if choosing not to take CDW (
https://www.avis.ie/media/filer_publ...conditions.pdf )
Some checks online suggest that a fee is not uncommon