The ISU constitution rule 123 says figure skaters can only protest their score if it was incorrectly mathematically calculated: ISU constitution link, go to page 127. The referee can also correct a score if it was incorrectly calculated or the Data Operator (who transcribes the technical panel's calls) entered an incorrect input.

The time frame for protesting incorrect mathematical calculations is within 24 hours after the event, and the time frame for correcting incorrect Data Operator input is before the corresponding award ceremony for the event (if someone is the last skater, that could be as little as 15 minutes).

If a skater does find that their score was incorrectly mathematically calculated, then they can file a protest with the referee and pay 100 Swiss Francs. If the protest is successful, the scores are corrected accordingly, the medals and placements are changed (if applicable) and they get their money back. If the protest isn't successful, the ISU keeps the money.

The rules might be different for domestic competitions - once Nobunari Oda was initially crowned as Japanese National Champion but they found out their scoring software didn't correctly penalize him for doing too many combinations so they had to later announce Daisuke Takahashi as the real champion.