FAQs: employers questions and answers: P45 has a 'Y' in the SL box but is for last year
The date of leaving a previous employment is irrelevant. If there is a ‘Y’ in the StudentLoans Box on the form P45 then you should start making deductions from the next pay- day.
Repayment of the Student Loan may continue for many years. Once a Start Notice has been issued deductions should continue until a Stop Notice is received, regardless of how many years have passed or what breaks in employment there have been
A new Start Notice is not issued to employers every year