Your student loan only ever looks at this month

You're thirtyish and the student loan line on your payslip has never quite made sense.

Income tax keeps a running total across the year. Your student loan doesn't. Each payslip is judged entirely on its own, and forgets the ones before it.

That one difference explains almost everything odd the deduction does, so it's worth thirty seconds even if you read nothing else here.

Your threshold is a monthly one, not a yearly one

Your annual threshold is divided by the number of payslips you get, and this month's pay is measured against this month's share of it.

Every plan has an annual figure you can earn up to before repayments start. Paid monthly, your threshold for the month is a twelfth of it. Paid weekly, it's a fifty-second. Your pay for that period is compared against that figure and nothing else.

Only the answer is rounded, never your pay

Nine per cent of the gap, then rounded down to the whole pound.

Once a payslip's earnings clear the period threshold, 9% of the difference comes off — 6% for a postgraduate loan — and that result is rounded down to a whole pound. It only ever rounds down, so it never works against you, and it's why the figure on your payslip is a whole number of pounds.

Two loans both come off, and the postgraduate one goes first

"First" is about bookkeeping, not about costing you more.

If you have a postgraduate loan alongside an undergraduate plan, both are worked out — each against its own threshold and rate — and both come off the same payslip. The postgraduate deduction is allocated first, but that only decides which loan the money is credited against. It changes nothing about the total leaving your pay, so it costs you nothing either way.

Being paid weekly and being paid monthly don't give the same answer

Same salary, same plan, slightly different totals over a year.

The threshold and the rounding both apply per payslip. Apply them fifty-two times instead of twelve and the small change falls differently. Neither one is wrong. It's the same rule, applied a different number of times.

A month you earn less is a month you repay less

The deduction can't reach back for it later.

Because nothing is cumulative, a lean month is simply a small deduction, and a good month is a larger one. There is no reckoning-up at the end of the year that comes after you for the difference — which is the reassuring half of the same fact that makes the weekly and monthly answers differ.

If you've overpaid across a whole tax year, it may be recoverable

Not automatically, though, and this calculator doesn't work it out.

If your income across an entire tax year — not any single payslip — comes in under your plan's annual threshold, you may be owed some of what was deducted. The Student Loans Company says it contacts people it identifies. If a tax year has ended and you haven't heard, you can ask them.

Where this breaks down

This page describes the deduction, not your balance.

What comes off your pay and what your loan is actually doing are two different subjects, and the second one is the student loan side of this site. Nothing here tells you whether you'll clear the loan, what interest is doing, or when it gets written off.

2026/27 tax year, from HMRC's payroll specification and internal manual. What the calculator assumes and what it doesn't try to do.