How does a copay differ from a deductible in health insurance? How does a copay differ from a deductible in health insurance? Copay is a percentage of the medical bill, while the deductible is a fixed amount. Copay is paid at each visit, while the deductible is an annual amount before insurance coverage starts. Copay is paid by the insurer, while the deductible is paid by the patient. Copay and deductible are terms used interchangeably in health insurance