CH153600 | Penalties for Failure to Pay on Time: Rules for specific taxes: Bank Payroll Tax (BPT): Penalties: Failure to pay all or part of amounts due - overview

From HM Revenue & Customs · Compliance Handbook

If a person fails to make a full payment of BPT by the due date, they become liable to a penalty on the amount unpaid.

The penalties for failing to pay BPT in full and on time are

an initial penalty of 5% for tax unpaid at the penalty date, see CH153620, and
two further penalties of 5% each for tax unpaid at 5 and 11 months after the penalty date, see CH153640.

So a failure to pay that continues for 11 months after the penalty date can incur all of these penalties on the same unpaid tax.

It is important to distinguish between

the due date - the date when the person needs to pay the tax, and
the penalty date - which is normally the day after the due date and the first date on which a penalty is chargeable for a tax period.

There are special rules for the penalty dates relating to determinations, assessments, corrections and amendments, see CH153700.