The owner doesn't necessarily pay all charges. The state pays for some.

AnimalProgressFixture
new case	Susie	Busboom
diagnosis	severe mastitis
order	intensive care
charge	100			diagnosis costs $100
check	balance	100
dead
order	pathology			pathology costs $80, but the state pays.
check	balance	180
check	balance	state	80
check	balance	Busboom	100

A clinician can have the clinic absorb some charges. Perhaps a test was done only for educational purposes, or the animal stayed an extra day.

AnimalProgressFixture
new case	2353	Peoria
order	intensive care
charge	100			Normal tests don't yield diagnosis
charge	900	clinic		absorb aggressive diagnosis charge.
check	balance	1000
check	balance	clinic	900
check	balance	Peoria	100
days pass	7			They're willing to let it go a week.
check	balance	Peoria	380
switch billing	clinic			Still no diagnosis - clinic takes over responsibility
days pass	3
order	discharge			Yay!
check	balance	1400
check	balance	clinic	1020
check	balance	Peoria	380