Penalties for Failure to Pay on Time: Rules for specific taxes: Pay As You Earn (PAYE) and National Insurance Contributions (NIC): Penalties: annual payment obligations - total penalties
The overall penalties for the tax year are the total of
- any initial penalty - 5% on tax unpaid at the penalty date, see CH152800
- any 5 month further penalty - 5% on tax unpaid 5 months after the penalty date, see CH152850, and
- any 11 month further penalty - 5% on tax unpaid 11 months after the penalty date.
See the example at CH152950.