Booked a Budget rental through Autoslash/Priceline. The price (Costco rate) included a second driver at no extra cost per the benefits listed when making the reservation. Even though I am not a frequent Budget renter (it’s been years) I have FastBreak and when we arrived at LAS, my name was on the board. At the exit gate I handed the guy the paperwork that was in the car and also my drivers license and my wife’s license. He handed hers back to me and said a second driver was not included (even though he acknowledged it would be free per the rate code) because there was no paperwork for her.

Not a huge deal; I guess I will be the designated driver for the weekend, but… how could I have had her added? Stand in line at the counter? There was a FastBreak booth in the garage, but it seemed deserted (10pm). Any way to make that happen ahead of time, online?

It's not necessary to add your wife as a second driver with Avis/Budget. Per their terms, spouses are automatically included as an authorized driver on the rental. They do not need to be explicitly added to the rental contract.

https://www.budget.com/en/help/usa-f...-driver-policy

Who Can Drive My Rental Car?

If your additional drivers meet any of the following requirements, then they are pre-authorized to be an additional driver for a rental car.

• They are the renter’s fellow employee or employer AND the car is being rented under a business account.
  
• They are the renter’s spouse or domestic partner.
  
• They are the companion driver for a renter with a disability who has filled out the non-licensed renter form.
  

No fee applies to additional drivers in the categories above, and they don’t have to fill out extra paperwork to drive the rental car.