When does a patient pay for a partial fill of their prescription?

The correct answer is aligned with how partial fills of prescriptions are typically handled, particularly in the context of controlled substances. When a patient receives a partial fill, they generally pay for the total amount of the medication that is ultimately dispensed, as payment systems often associate prescription costs with the dispensing transaction rather than the fulfillment schedule.

In this case, option B indicates that the patient pays after receiving the second partial fill, which reflects the common practice wherein the patient may complete their obligation for the total prescription cost with the final fill. This allows for accurate billing based on the actual quantity of medication dispensed across all partial fills.

In situations where patients receive only partial fills at the first fill, the pharmacy or billing system might treat the entire prescription cost as a single transaction to avoid complications in tracking partial payments. Therefore, it's not accurate for patients to be charged at the time of the first fill or after the first partial fill without considering the total quantity they eventually receive. Furthermore, the notion that a patient would never pay for a partial fill does not align with the typical financial and regulatory practices in pharmacy settings.