PAYE70020 | PAYE operation: aspects of PAYE operation - employer: pay below NIC primary threshold but at or above lower earnings limit
From HM Revenue & Customs · PAYE Manual
If an employee's rate of pay is below the Primary Threshold for National Insurance contributions (NICs) but at or above the Lower Earnings Limit, the employer must
Prepare a Deductions Working Sheet entering NI in the code space and contribution table letter
Use the Deductions Working Sheet to record pay and National Insurance contributions only. Pay must be totalled on the Deductions Working Sheet at the end of the year or when the employee leaves
Complete and submit a form P14