How Student Loan Repayments Are Calculated

It is a graduate tax in all but name

Most people assume a student loan works like a mortgage or a car loan: you borrowed a set amount, and you pay it back in instalments until it is cleared. UK student loans do not really work that way. What you repay each month has almost nothing to do with how much you borrowed. It is calculated as a percentage of your income above a threshold, deducted automatically if you are employed, in a similar way to National Insurance.

This means your monthly repayment depends entirely on how much you earn, not on your outstanding balance. Someone who borrowed a small amount and someone who borrowed a very large amount, on the same salary and same plan type, will repay exactly the same amount each month. The difference shows up only in how long it takes to clear the loan, and whether it gets written off first.

The plan types

Which rules apply to you depends on when and where you studied, not on when you happen to be repaying. The main categories are:

• Plan 1: mostly pre-2012 English and Welsh students, and some Northern Ireland students.
• Plan 2: most English and Welsh undergraduates who started between 2012 and the introduction of Plan 5.
• Plan 4: Scottish students.
• Plan 5: newer English undergraduates under the current system.
• Postgraduate Loan: separate rules for postgraduate master’s and doctoral loans.

Each plan has its own repayment threshold, the income level above which you start paying anything at all, and its own interest rate rules. These thresholds and rates are reviewed and can change, so rather than quoting a figure here, the golden rule is to check your specific plan on the official gov.uk student finance repayment pages, since using the wrong number for the wrong plan is one of the most common sources of confusion.

If you are not sure which plan you are on, your loan statement from the Student Loans Company will state it clearly, and it is worth confirming before you make any assumptions about what you should be repaying.

How the calculation actually works

The basic mechanics are the same across plans, only the threshold and percentage differ:

1. Take your income for the relevant period (this is usually gross income before tax for employees, or profit for the self-employed).
2. Subtract the repayment threshold for your plan.
3. Anything above that threshold is multiplied by the repayment percentage, typically in the region of nine per cent for standard undergraduate plans, with postgraduate loans usually calculated at a lower separate percentage on top if you have both types.
4. That amount is what gets deducted, usually spread across the year via PAYE if you are employed.

Crucially, this is calculated on income above the threshold, not on total income. So if your income is only slightly above the threshold, you pay a modest amount; if it is well above, you pay proportionately more. It works in a similar step-like way to income tax, though the mechanics and thresholds are entirely separate from tax bands.

If you have income from more than one job, or fluctuating self-employed income, the annual reconciliation through Self Assessment can adjust what you have paid through the year, which is why some people find they owe a top-up or are due a partial refund after their tax return.

Employed versus self-employed

If you are an employee, your employer calculates and deducts student loan repayments automatically through PAYE, based on your pay in each pay period, and reports this to HMRC, who then pass the money to the Student Loans Company. You do not need to do anything unless something looks wrong on your payslip.

If you are self-employed, repayments are instead calculated once a year through Self Assessment, based on your profits for the tax year, and paid alongside your income tax and National Insurance bill.

Interest, overpayment and write-off

Interest is added to the loan balance while it remains outstanding, and the rate depends on your plan and sometimes your income, since some plans use a sliding scale linked to earnings. Because repayments are based on income rather than balance, interest can sometimes accrue faster than you are repaying it, particularly early in a career, which is normal under this system rather than a sign of a problem.

Every plan is eventually written off after a set number of years from when you started repaying or from the April after you left your course, regardless of how much is left outstanding. This means many graduates never clear the balance in full and are not expected to. Voluntary overpayments are allowed if you want to clear the loan faster, but for many graduates, given the write-off rules, this is a personal decision rather than a financial necessity, and worth thinking through carefully rather than doing automatically.

Checking your own numbers

Because thresholds, interest rates and percentages are reviewed and can change, always check your current plan’s figures directly with the Student Loans Company or gov.uk before making assumptions about your own repayments, and use MoneyHelper’s independent guidance if you want a neutral explanation of whether overpaying makes sense for your circumstances.