1. Rights of the Office to the payment of fees shall be barred four years from the end of the calendar year in which the fee fell due.
2. Rights against the Office for the refunding of fees or sums of money paid in excess of a fee shall be barred after four years from the end of the calendar year in which the right arose.
3. The periods laid down in paragraphs 1 and 2 shall be interrupted, in the case covered by paragraph 1, by a request for payment of the fee and, in the case covered by paragraph 2, by a reasoned claim in writing. On interruption it shall begin again immediately and shall end at the latest six years after the end of the year in which it originally began, unless in the meantime judicial proceedings to enforce the right have begun. In this case the period shall end at the earliest one year after the judgment has acquired the authority of a final decision.