CTSA: penalties for late returns: determination: general rules
You can make a further determination of a penalty on discovery that the penalty in the original determination is, or has become, insufficient (TMA70/S100 (6)). This will be the case, for example, when the tax ‘base’ for the penalty increases.
If you reduce the tax ‘base’ for a tax-related penalty, you must reduce the penalty determination to reflect the correct amount of unpaid tax whether or not the determination is under appeal (TMA70/S100 (5).
When more than one tax-related penalty type is chargeable on the same slice of tax see CTM94240.
A penalty determined under TMA70/S100 is due and payable 30 days after the date on which the notice of determination is issued. It is then treated for collection and recovery purposes as tax charged in an assessment that is due and payable.
There is no interest chargeable on any CT penalties.