Thomas Zordani flew from his home in Denver to Phoenix for a consultation with a Mayo Clinic neurosurgeon, hoping to find out what could be done to treat his debilitating headaches after worrisome brain scan findings.

When making the appointment, Zordani said, he’d been told the clinic was in his insurer’s network. Upon arrival, Zordani was summoned to the clinic’s financial office and told he had to make a $5,000 preservice deposit, because Mayo had since determined it did not accept his insurance. He was automatically designated “self-pay,” even though his plan had out-of-network benefits.

Not having that kind of cash on hand — and angry on principle — he refused. His appointment was canceled.

“I was so livid,” Zordani said, recalling that day in early April 2024. He later learned that Mayo had sent a message to him in his insurance carrier’s patient portal shortly before his visit with an estimate of the cost: $565, not the larger amount it later demanded.

Traditionally, patients usually receive bills for their share only after getting treatment. But what Zordani faced is becoming increasingly common — hospitals or other medical providers seeking prepayments.