This question is actually a moot point, as I moved my horse to a different stable and use a different vet practise now, but I am just curious.
Horse needed some work done on her teeth and the vet who did the barn call said that this needed to be done at their clinic rather than at the stable. In my experience, most vets/dentists can do quite a bit of dental work on-site but whatever, I arranged transport and took the horse to the clinic, where the work was done. All fine. Then the secretary explained that before the horse left their premises, all bills had to be settled, right there and then. They would not wait for you to sort it out with your insurance company, remortgage your house, or sell your children. I did a bit of a double-take, as I had never encountered this before, and said, "Even for major surgery?" "Yes," she answered, explaining that they got fed up chasing people up for bills so this was their policy.
The bill in question was only about £200, which was doable, but I was a bit traumatized by the fact that if your horse went in for colic surgery, would you really have to cough up £5000 on the spot? Yikes!
I've not run across this with any other vet, who would let you pay it off and usually leave you plenty of time to deal with your insurance company. Have you?