Nearly seven months after the fatal shooting of an insurance CEO in New York drew widespread attention to health insurers’ practice of denying or delaying doctor-ordered care, the largest U.S. insurer

Prior authorization requires a medical provider to receive approval from an insurer before treating patients or prescribing medication. Without prior authorization, insurers can refuse to pay for treatment or medication.

The nation’s major health insurers are promising to scale back and improve a widely despised practice that leads to care delays and complications.