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 monthly threshold isn't your annual threshold divided by twelve

It is, but it's rounded down to the penny first, and that rounding is the whole point.

Every plan has an annual threshold you can earn up to before repayments start. HMRC turns that into a per-payslip figure by dividing it down and rounding down to the penny. Your earnings aren't rounded at all. Only the threshold is, and then the deduction at the end.

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's a common and reasonable assumption that your earnings get rounded first, before the sum. They don't. The rounding happens once, at the end, and always downwards — so it never works against you.

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.

I can't tell you what to do about your own pay. I don't know your situation, and this is information rather than advice.

2026/27 tax year, from HMRC's payroll specification and internal manual. What this calculator assumes and doesn't handle.