Penalties for Failure to Pay on Time: Rules for specific taxes: Income Tax and Capital Gains Tax (IT & CGT): Penalties: Failure to pay all or part of amounts due - total penalties
The overall penalties for the return period are the total of
- any initial penalty - 5% on tax unpaid at the penalty date, see CH155120,
- any 5 month further penalty - 5% on tax unpaid 5 months after the penalty date, see CH155140, and
- any 11 month further penalty - 5% on tax unpaid 11 months after the penalty date.
See the example at CH155180.