To add your Hertz Gold Plus Rewards number to an existing reservation in 2026, the most reliable method is to log in to your Hertz account and use the "Modify" feature under "Find a Reservation." If you booked directly on the Hertz website without being logged in, enter your confirmation number and last name; once the reservation appears, you can look for an "Add Loyalty Number" field. However, if you booked through a third-party site like Expedia or Priceline, the system often locks the profile, preventing digital updates. In this case, you must call Hertz Customer Support or ask the agent at the rental counter to manually attach your Gold number before the contract is printed. It is crucial to do this before you pick up the car to ensure you get your "Gold" benefits, such as bypassing the counter or earning points. Note that adding a number at the counter might not allow you to use "Gold Canopy" (direct to car) service for that specific trip, as that usually requires the profile to be attached at least 24 hours in advance.