Should you voluntarily overpay your student loan or invest the money instead? The answer hinges on one critical question.
Student Loan Overpay vs Invest Comparison
Will loan be written off WITHOUT overpaying?
Baseline write-off / payoff year
With overpayment — new payoff date
Interest saved by overpaying
Investment pot (same money invested)
Net benefit of overpaying vs investing
5-year projection
Illustrative only. Investment returns are not guaranteed. Plan 2 interest rate: RPI+3% (7.3% used). Plan 1/4: 1% above BoE base (5.25% assumed). Plan 5: RPI only (4.3% assumed). Postgrad: RPI+3% (7.3% used). This is not financial advice.
The Critical Question: Will Your Loan Be Written Off?
This is the single most important factor. If your loan will be written off at the end of your repayment term (because your earnings mean you will not repay it in full), then voluntary overpayments are largely wasted — you are paying back money that would have been forgiven. The "interest" you save on a written-off loan is not real cost to you.
If, on the other hand, you are certain to repay your loan in full before write-off, then overpaying does save real interest — and the comparison becomes about whether those interest savings exceed what you could earn investing instead.
Student Loan Plan Summary
Plan 1 (pre-2012 or NI): threshold £24,990, rate 1% above BoE base rate, no write-off date (cleared at 65)
Plan 2 (post-2012 England/Wales): threshold £27,295, rate RPI+3% max, write-off after 30 years
Plan 4 (Scotland): threshold £31,395, rate 1% above BoE base, write-off at 65
Plan 5 (post-Aug 2023 England): threshold £25,000, rate RPI only, write-off after 40 years
Postgraduate: threshold £21,000, 6% repayment rate, RPI+3%, write-off after 30 years
Frequently Asked Questions
Should I pay off my student loan early or invest? +
It depends on whether your loan will be written off. If your loan is likely to be forgiven, investing is almost always better — overpaying a loan that would have been cancelled is wasted money. If you will repay the loan in full anyway, compare the interest rate on your loan to investment returns.
When does overpaying a student loan make sense? +
Overpaying only makes financial sense if you are certain the loan would be fully repaid before write-off anyway. For most Plan 2 borrowers with large balances and average earnings, the loan will be written off — making overpayment financially unwise.
What is the Plan 2 student loan write-off date? +
Plan 2 loans are written off 30 years after the April you first became due to repay, or when you reach age 65 (whichever is earlier). Any outstanding balance at that point is cancelled and not taxable.
Does overpaying reduce my monthly repayments? +
No. Overpaying does not reduce your mandatory monthly repayments. Your monthly repayment is always calculated as a percentage of income above the threshold. Overpayments only reduce the outstanding balance and future interest accrual.
Can I get a student loan overpayment refunded? +
No. Once you make a voluntary repayment to the Student Loans Company, it cannot be refunded. This is why the overpay vs invest decision is so important — overpaying a loan that would have been written off is an irreversible financial mistake.
How does investment return compare to student loan interest? +
Long-term stock market returns have historically averaged 7–9% per year. Plan 2 interest runs at up to RPI+3% (around 6–8% recently). However, for loans likely to be written off, comparing interest rates misses the point — the key question is the write-off probability.
What is Plan 5? +
Plan 5 applies to English students starting courses from August 2023. The threshold is £25,000/year, the repayment rate is 9% above threshold, interest is RPI only (no plus 3%), and the write-off period is 40 years — more favourable terms than Plan 2.
Is a Stocks and Shares ISA the best place to invest instead? +
A Stocks and Shares ISA is one of the most tax-efficient ways to invest in the UK — returns are free of capital gains tax and income tax. The annual ISA allowance is £20,000. For long-term investing to compare with student loan repayment timescales, a low-cost globally diversified index fund held inside an ISA is a commonly recommended approach.
What if I have both an undergraduate and Postgraduate loan? +
Run the analysis separately for each loan. Both are repaid simultaneously from income but at different thresholds and rates. Prioritise whichever analysis reveals the higher risk of paying back a loan that would otherwise have been written off.
Is the 5-year projection reliable? +
The projection uses constant assumptions for salary growth and investment return. Real outcomes will vary. Treat it as illustrative. The most reliable insight this calculator provides is the write-off question — which you can assess with confidence even under different salary scenarios.
What about building an emergency fund first? +
Financial advisers typically recommend having 3–6 months of expenses in accessible savings before considering overpaying loans or investing. A student loan overpayment cannot be retrieved in an emergency, while an emergency fund can. Build your safety net before either overpaying or investing surplus income.
Where can I get official advice? +
The Student Loans Company and Student Finance England provide official information on repayment terms. The Money and Pensions Service (moneyhelper.org.uk) offers free guidance. For regulated investment advice, use an FCA-authorised financial adviser.