We refund a charge when it was our mistake:
A duplicate charge — the same amount charged twice for the same thing. We refund the extra one. Automatic when our records show a second charge, within 72 hours, for something the first one already paid for.
A charge after you cancelled — a subscription charge created after your cancellation. Refunded in full, automatically.
Priority Review never turned on — you paid, but your application isn't on the priority shortlist. Refunded in full, automatically.
The wrong amount — charged more than the checkout showed. A person checks it and refunds the difference.
A charge you didn't make — a person looks into it and refunds a charge that wasn't authorised.
Start any of these at /help/change-request.
Send a change request: billing mistakes our records prove are refunded automatically, and a person answers the rest within two business days.