Plan 2 Interest Is 6.2% and the Balance Outgrows the Payments — Clear the Loan

Plan 2 interest is set at the Retail Price Index plus up to 3%, capped at a prevailing market rate. For anyone earning £52,885 or above, the full rate applies. Gov.uk's student loan interest page lists the current Plan 2 rate at 6.2% for high-earning borrowers, with a sliding scale starting at 3.2% from £29,385.

6.2% is not a number to brush aside. The Bank of England base rate sits at 3.75%. The best fixed-rate cash ISAs pay around 4.5%. A two-year fixed mortgage at 75% LTV averages 5.14%. Plan 2 interest comfortably exceeds all of them.

And it compounds. The £40,000 balance becomes £42,480 after year one of accrued interest before any repayment. The minimum £1,855 brings it back to £40,625 — meaning the balance has actually grown by £625 despite a full year of payments. This is what "running on the spot" looks like financially. Carry on for a decade and you have repaid £18,550 and owe more than you started with.

No investor would accept this on any other debt. We pay off credit cards at 22% because the rate is intolerable. 6.2% is lower, but the principle is identical: capital eroded by compounding interest is capital you will never recover.

The "30-year write-off" defence assumes you stay below threshold for most of your working life. For a current graduate following a normal career arc — a few promotions, a couple of job changes, maybe a side hustle — that assumption falls apart fast.

The modal earner in their 30s with a degree earns around £40,000 to £50,000 today. By their 40s, mid-career, that climbs to £60,000 to £80,000 for many professions. The Department for Education's own modelling, published in its analysis of the 2023 student finance reforms, shows that under the Plan 5 system around 65% of graduates will repay in full or near-full. Plan 2's 30-year write-off catches a larger share, but the cohort still expected to clear the loan is substantial — and it tracks tightly with above-median earners.

If you are reading a personal finance article about whether to overpay your loan, you are statistically near-certain to be in the cohort that will repay it. The relevant question is not "will the write-off bail me out?" — it is "how much extra interest will I have paid over 25 years of minimum repayments before I clear it anyway?"

The answer, for a £40,000 balance at 6.2%, is roughly £35,000. That is the cost of choosing the minimum over the accelerated path.

Take the same £50,000-earner with £40,000 outstanding. Statutory minimum: £155 a month, or £1,855 a year. Interest at 6.2% on the running balance.

Minimum repayments only. At a £50,000 salary frozen in real terms, the loan is cleared after roughly 28 years. Cumulative payments: around £51,900. Of that, £40,000 paid down the principal; £11,900 went on interest. Worse, if your salary rises in line with average wage growth (around 3% real), you climb into higher repayment bands and the 9% deduction grows — but the interest rate also climbs to the full 6.2%, accelerating the balance. Real-world modelling for a graduate moving from £50,000 to £75,000 over 20 years puts total interest closer to £35,000 over the life of the loan.

Accelerated: extra £400 a month. Same £50,000 salary, but £555 a month total going to the loan (£155 statutory plus £400 voluntary). The £40,000 clears in around six and a half years. Cumulative payments: roughly £43,000. Of that, £40,000 paid down the principal; only £3,000 lost to interest.

Difference: £32,000 of interest avoided over the life of the loan. That is real money you keep, not modelled returns from an investment that may or may not deliver. Once cleared at year 6.5, you redirect the same £555 a month to a SIPP for 24 years. At 5% real growth, the SIPP builds to around £315,000 — without the drag of an accruing loan in the background.

The "invest the difference" case rests on three fragile assumptions: that markets deliver 5% real returns reliably, that you are disciplined enough to invest the saved money rather than spend it, and that you would have made those SIPP contributions either way.

Real equity returns over the last 25 years have run closer to 4% real after fees, not the textbook 5%. The FTSE All-Share has delivered around 4.2% real annualised since 2000, with significant drawdowns along the way. A 2000-2010 starter saw negative real returns over their first decade. The 6.2% guaranteed return on loan repayment is not just attractive — it is risk-free, immediate, and tax-paid.

The behavioural question is harder still. The vast majority of people who plan to "invest the difference" do not. The £400 a month gets absorbed into living costs, holiday upgrades, a slightly nicer car. Studies of windfall behaviour and increased disposable income show stunningly low conversion into long-term investment. The optimizer case assumes you behave like a robot. Most people do not.

Finally, the SIPP relief argument cuts both ways. You can pay the loan down AND fill a SIPP — these are not mutually exclusive. The question is which to do first when budgets are limited. Once the loan is cleared, your gross take-home rises by the avoided 9% deduction, and that windfall can fund the SIPP catch-up. You have not lost the relief; you have deferred it by six years for a guaranteed 6.2% return.

After payoff, the 9% threshold deduction stops. For someone earning £55,000, that is £2,304 a year of net pay — £192 a month — returning to your bank account. This is permanent, not a one-off.

That freed cash flow is what compounds. From age 43 to 67 — 24 years — £192 a month into a SIPP at 40% relief becomes £320 gross. At 5% real growth, the pot reaches £143,000. Add the £400 a month voluntary contribution you previously sent to the loan, and total monthly SIPP contributions rise to £720 net or £1,200 gross. Total pot at 67: around £540,000.

This is similar to the optimizer's projected figure — but with one crucial difference. The Guardian's pot is built on a debt-free balance sheet. No accruing 6.2% interest line. No "will I hit write-off?" anxiety. No statutory deduction shadowing your payslip into your 60s. The optimizer's projected SIPP pot ignores the cumulative £35,000 of interest paid over the same period. Strip that out of the comparison and the two strategies converge.

The Plan 2 loan repayment is one of the few near risk-free 6.2% returns available to a UK saver. You cannot get 6.2% guaranteed in a cash ISA. You cannot get 6.2% in a 10-year gilt — the current yield sits around 4.9%. You cannot get it without taking equity risk, which means accepting drawdowns of 30% to 50% along the way.

Your pension and ISA returns are uncertain. Your future income is uncertain. The fiscal treatment of the loan itself is uncertain — Plan 2 borrowers have seen interest rate methodology changed mid-flight, thresholds frozen below inflation, and write-off periods extended for newer plans. Anything the government changed once it can change again, and the current 30-year window is not a constitutional guarantee.

Clearing a guaranteed 6.2% liability is the closest thing to alpha most savers will ever see. Take it. Then build the ISA and the SIPP on a clean balance sheet, free of a compounding 6.2% drag in the background.

For more on the mechanics, see our student loan repayment guide. For the SIPP relief case, see our ISA versus pension allocation piece. The optimizer's counter-argument makes the case for treating the loan as a graduate tax — both views have merit, but the maths above is unsentimental for above-median earners.

This article is for informational purposes only and does not constitute financial advice. Student loan interest rates, thresholds, and write-off rules are subject to change by HMRC and the Department for Education. You should seek independent financial advice before making any investment or debt repayment decisions.