You should make Student Loan deductions for any pay periods in which the borrower's earnings exceed the threshold.
Do not take account of previous earnings as the deductions are non-cumulative.
If, after the end of the year, the borrower can prove that he or she earned less than the threshold a repayment of any deductions paid may be made by the Student Loans Company.
Any repayment in these circumstances is a matter between the borrower and the Student Loans Company.
Note: The employer should never be told to phone the Student Loans Company. They will deal only with the borrower.