FAQs: employers questions and answers: t/p paid every 4 weeks. how do I work out dedns?
Your payroll software will work out the deductions for you.
If the earnings period is a non-standard or irregular period and your software is unable to do the calculation (this will be very rare) you can use the manual student loan deduction tables (SL3). These tables will show you, step by step, how to calculate the deductions on a proportionate basis and can be found at http://www.hmrc.gov.uk/payerti/forms-updates/forms-publications.htm
The deductions are non-cumulative. Look only at the current pay period. Don’t worry about previous earnings.