After notice has been served of the determination of a penalty, the determination cannot be altered except in accordance with this paragraph or on appeal.

If it is discovered by an authorised officer that the amount of the penalty is or has become insufficient, the officer may make a determination in a further amount so that the penalty is set at the amount which in the officer’s opinion is correct or appropriate.

If in the case of a tax-related penalty it is discovered by an authorised officer that the amount taken into account as the amount of tax is or has become excessive, he may revise the determination so that the penalty is set at the amount that is correct.

Where more than the correct amount has already been paid the appropriate amount shall be repaid.

In this paragraph an “authorised officer” means an officer of the Board authorised by the Board for the purposes of this paragraph.