BPP Q 41 section a

You should assume today’s date is 30 November 2022.

John is a new client whom you met today. On 6 April 2021, he commenced in self-employment and prepared his first set of accounts to 5 April 2022. John had not previously filed a self-assessment tax return and has not received any communication from HM Revenue & Customs (HMRC) about his tax affairs. As this will be his first self-assessment tax return, John is also concerned that HMRC might carry out a compliance check.

i)

Advise John of the latest date by which he should have notified HMRC of his chargeability to income tax for the tax year 2021/22 and the maximum and minimum penalties for late notification if he immediately notifies HMRC of his chargeability and is deemed to have been careless.

Here , John should have notified HMRC within 6 months , so 6 OCT
He is two months late

min penalty in case of carelessness 30%

“if John tells HMRC of his failure to notify within 12 months and John has no reason to believe HMRC has discovered, or is about to discover, the error (unprompted disclosure) as appears to be the case here, the penalty can be reduced by HMRC to 0%”

I did not understand this statement , failure to notify within 12 months ?