Should You Pay Off Student Loans or Invest First?

About the examples in this guide: the people, jobs and figures used in the worked examples are illustrative scenarios we created to show how the rules and numbers work. They are not accounts of real individuals. Always check current rules and your own circumstances.

Should You Pay Off Student Loans or Invest First?

By the First Wage Editorial Team · Published 29 September 2026 · 8 min read

The Short Answer

For most people on Plan 2 or Plan 5, putting spare money into a Stocks & Shares ISA rather than overpaying a student loan works out better financially, because most graduates on these plans never fully repay before their loan is written off — meaning voluntary overpayments often just hand money to a balance that was going to disappear anyway. The exceptions are high earners on a clear path to repay their loan in full before write-off, and people for whom being debt-free carries a psychological value that’s worth more to them than the maths. There’s no universally correct answer — but there is a clear framework for working out which camp you’re in.

Josh’s Pay Rise Dilemma

Josh, 26, works in digital marketing in Manchester and just got a pay rise that leaves him with roughly £200 extra a month after bills. His instinct, shared by a lot of people his age, was to throw it straight at his Plan 2 student loan, which currently sits around £34,000. It felt responsible. It felt like the “adult” thing to do — treat debt as the enemy, kill it as fast as possible.

Then a colleague mentioned she’d done the maths on her own loan and worked out she was on track to be written off with tens of thousands still outstanding regardless of what she did, and that every pound she’d overpaid in her twenties had essentially been wasted. Josh had never actually run the numbers on his own situation. He’d just assumed debt was debt.

This is the exact question worth pausing on before moving a single pound: is your student loan actually a debt you’re at risk of fully repaying, or is it closer to a fixed monthly tax that will eventually be written off no matter what you do?

Step One: Work Out Whether You’re a “Repayer” or a “Write-Off” Case

This is the single most important input into the whole decision, and it depends almost entirely on your likely lifetime earnings relative to your loan balance and plan.

There’s no shame in not knowing which camp you’re in — most people don’t, because nobody ever sits them down and explains that this is even a relevant question. A rough gut-check: if you’re confidently earning well above the Plan 2 threshold of £29,385 (or Plan 5’s £25,000) with strong prospects for continued growth, lean toward “likely repayer.” If your income is closer to or below the threshold, or growth is uncertain, lean toward “likely write-off.”

Step Two: If You’re Likely a Write-Off Case, Investing Usually Wins

If your loan is very unlikely to be fully repaid before write-off, overpaying it delivers you no benefit at all — you’re not shortening your working life of repayments (that’s driven by income and threshold, not balance) and you’re not saving on interest that will ever actually cost you anything, since write-off cancels it regardless. In this scenario, spare money in a Stocks & Shares ISA, left to compound over years or decades, is very likely to leave you meaningfully better off than a graduate who overpaid instead. A Stocks & Shares ISA also comes with the added benefit of being genuinely accessible if you need the money for a house deposit, an emergency, or anything else — money paid into a student loan is gone, with zero flexibility to get it back.

Where £200/month is likely to do more, over 10 years

Overpay loan (write-off case)
Low benefit
Stocks & Shares ISA
High benefit

This is illustrative, not a forecast — investment returns are never guaranteed, and markets can fall as well as rise. But over long time horizons, and specifically compared against a “debt” that was never going to be fully repaid anyway, the case for investing is usually strong.

Step Three: If You’re Likely a Full Repayer, the Calculation Changes

If your income trajectory suggests you’ll clear the loan in full before write-off, the picture flips. In this case, your student loan is functioning as a genuine long-term debt, and the RPI-linked interest is a real cost you’ll actually pay, not a number that gets erased. Here, the comparison becomes a more conventional one: is the guaranteed “return” of paying down interest-bearing debt better than the expected, but not guaranteed, return of investing? For high earners with high loan balances and strong repayment prospects, overpaying can genuinely make sense, particularly if the interest rate on the loan is running high relative to likely investment returns.

Step Four: Factor In the Psychological Piece Honestly

The framework above is about maximising money. It isn’t the whole picture for everyone. Some people find carrying any form of debt — even income-contingent, largely-theoretical, write-off-eligible debt — genuinely stressful in a way that affects their wellbeing, their decision-making, or their sense of financial freedom. If that’s you, there’s a legitimate argument for overpaying even when the purely financial maths favours investing, because the value of peace of mind is real, even if it’s hard to put a number on. The key is making that choice knowingly, rather than overpaying by default because it feels responsible without ever checking whether the numbers actually support it.

Step Five: Don’t Forget the Basics Come First

Whichever camp you’re in, a few things should generally happen before either overpaying a loan or investing seriously: build a small emergency fund (a few months of essential costs) in an easy-access savings account, clear any high-interest consumer debt like credit cards, and make sure you’re capturing any employer pension contribution match, since that’s an immediate guaranteed return that beats almost anything else on this list.

First Wage Takeaway

Work out honestly whether your income trajectory makes you a likely full repayer or a likely write-off case — that single question determines almost everything else. For most people on Plan 2 or Plan 5, that answer points toward investing spare money rather than overpaying a loan that was largely going to be written off anyway.

Frequently Asked Questions

Is it ever a bad idea to overpay a student loan?

Yes, if you’re unlikely to fully repay it before your write-off date, overpaying effectively gives money to a debt that would have been cancelled anyway, with no benefit to you.

How do I know if I’ll repay my loan in full before write-off?

There’s no certainty, but a rough guide is to compare your current and expected future income against your plan’s threshold and balance. High, fast-growing salaries relative to the balance suggest a repayer profile; moderate or flat income suggests a write-off profile. Online student loan calculators from MoneyHelper can help model this against your specific numbers.

Does a Stocks & Shares ISA guarantee better returns than paying off my loan?

No, investment returns aren’t guaranteed and can go down as well as up. The comparison is about likely long-term outcomes and flexibility, not a certainty in either direction.

What should I do before deciding between investing and overpaying?

Build a small emergency fund, clear any high-interest debt like credit cards, and make sure you’re getting your full employer pension match first — these generally come before either option.

Related Guides

Sources and further reading

Last updated: 8 October 2026. Rules, rates and thresholds change, so check the official sources above before making decisions. This guide is general information, not personalised financial advice.