Student loan deductions are worked out each payday, not once a year. That simple rule explains most of the surprises people see on their payslips: a deduction in a bonus month, nothing at all across two part-time jobs, or a figure that does not match a yearly calculation.
Your employer compares the pay for each period with the weekly or monthly threshold for your plan. For Plan 5 in 2026/27 that is £480 a week or £2,083 a month (HMRC's payroll figures are £480.76 and £2,083.33). If that period's pay is over the line, 9% of the excess is taken. GOV.UK says you will make a repayment if your income goes over the weekly or monthly threshold, for example because of a bonus or overtime.
Someone on Plan 5 earns £23,000 a year, so normally £1,916.67 a month. That is under £2,083, so nothing is taken. In March they get a £1,000 bonus, so March pay is £2,916.67. Payroll takes 9% of £833.67, which is £75.03, so about £75.
Their income for the year is £24,000, below the £25,000 yearly threshold. GOV.UK says you can ask for a refund at the end of the tax year if your annual income was less than the yearly threshold for your plan. The refund can only be paid after the SLC has confirmed your income with HMRC, which happens after the tax year ends.
The same applies to overtime. If your basic pay is under the monthly threshold but some months include overtime that takes you over, you will see deductions in those months only. If your total for the year ends up over £25,000, you may have repaid slightly less than 9% of the yearly excess, because the quiet months under the threshold count for nothing. HMRC tells employers not to make deductions in arrears.
GOV.UK says that if you have more than one employer, you only make repayments from jobs where you are paid over the threshold, not on your combined income. HMRC's employer guidance tells each employer to ignore earnings from other employers.
Example: a Plan 5 borrower has two jobs paying £1,600 and £1,300 a month. Together that is £34,800 a year, but neither job is over £2,083 a month, so no repayments are taken through payroll. With one job paying £2,500 and another £500, repayments are taken only from the first: 9% of £417, which is £37.53, so about £37 a month.
If you also complete a Self Assessment return, the picture changes. GOV.UK says HMRC then works out your repayment from the return, based on your income for the whole year. See Plan 5 and Self Assessment.
If you are paid weekly, the weekly threshold applies. For other pay intervals, payroll software applies the matching threshold for the period. If your pay interval changes, for example from weekly to monthly, HMRC tells employers to work out the deduction for the new period, which can make one payslip look odd.
HMRC tells employers to work out student loan deductions on the same gross pay figure they use for employer Class 1 National Insurance. A salary sacrifice arrangement reduces the cash pay you are entitled to, usually in return for a benefit such as an employer pension contribution. Where that lowers the pay figure used for National Insurance, the student loan deduction is worked out on the lower figure too. Pension contributions that are simply taken from your pay, without a change to your contract, are a different arrangement, so check with your employer which you have.
Through Self Assessment, GOV.UK says HMRC uses your total annual income, including any pension income you receive.
Your final pay from a job is tested in the same way, so holiday pay or a final payment can trigger a deduction. Your P45 tells your next employer whether deductions should continue. If you have a gap before the next job, nothing is collected for the gap.
Our refund guide explains how to claim each one.
The calculator works on yearly income. For an irregular year, enter your expected total for the year to see the yearly picture.
Sources: GOV.UK: how much you repay · GOV.UK: when you start repaying · HMRC: student loan guidance for employers · HMRC: salary sacrifice for employers · GOV.UK: getting a refund. Checked 29 October 2026.
Last checked: 29 October 2026. Estimates only, not financial advice.
Each pay period is tested against the monthly or weekly threshold. A bonus can take one month over £2,083 even if your yearly pay is under £25,000.
Not through payroll. GOV.UK says you only repay from jobs that pay over the threshold, not on combined income. Self Assessment uses your total income for the year.
You can ask for a refund after the tax year ends, once the SLC has confirmed your income with HMRC.