NIM21042 | Class 2 National Insurance Contributions: Small Earnings Exception: Duration of exception: Backdating into a previous tax year
From HM Revenue & Customs · National Insurance Manual
Regulation 44 of the Social Security (Contributions) Regulations 2001 (SI 2001 No. 1004)
Exception was not normally backdated into a previous tax year unless the application was made less than 13 weeks into the new tax year and the contributor requested it.