The beginners’ guide to money market funds
Mark Tovey is a finance journalist with bylines in The Guardian, The Motley Fool, and more. He digs into data and FOI-based investigations, and makes finance easier to understand.
Last updated 25th February 2026
9 min read
- Money market funds invest in short-term, low risk debt.
- They’re highly liquid, giving good flexibility for cash storage, but are not FSCS protected like savings accounts.
- Money market funds are influenced by short-term interest rates, reacting quickly to rate hikes but adjusting more slowly when rates fall.
- They can be opened within ISAs and SIPPs for tax efficiency, but also inside a regular General Investment Account.
- They’re available through a range of providers, each offering different fund options, fees and features.
Financial Interest provides guidance, not advice. If you’re unsure about anything, speak with a qualified adviser. When investing, your capital is always at risk. Past performance does not guarantee future results.
What is a money market fund?
Money market funds, commonly shortened to 'MMFs', are mutual funds and ETFs that earn interest by investing in short-term debt from stable governments, banks, and top-rated businesses.
They prioritise liquidity (being able to get your money out easily) and safety (not losing all your money) while offering modest returns.
They offer lower risk than stocks or property, while typically paying out more than the average easy-access savings account. This can be the difference of only a fraction of a percent, or more, depending on the savings account you're comparing to.
Unlike savings accounts, these investment products aren't protected by the Financial Services Compensation Scheme (FSCS).
Money market funds in the UK and EU have to follow strict rules to keep your money safe and accessible. For example, at least 30% of the fund must be in investments that can be turned into cash (they 'mature') within a week.
And to avoid putting too many eggs in one basket, they’re not allowed to invest more than 5% in any single company or bank, unless it’s a government bond or an overnight deposit with a bank. These rules help the fund stay stable, usually keeping each unit worth around £1. This £1 value is important to retain.
Main types of money market funds
- Short-term funds: Invest in things that get paid back quickly.
- Standard-term funds: Hold slightly longer-term loans and might earn a tiny bit more interest.
- Public debt funds: Almost entirely invested in government-backed stuff, so they’re considered to be the safest option.
Why use an MMF?
You're probably thinking: if I don't get much more in interest, and my funds aren't protected, why wouldn't I just stick with my fixed-rate savings account or cash ISA?
Well, you can do exactly that. But interestingly, banks often invest your savings in short-term government and commercial debt themselves, but instead of passing on the full returns, they pocket a cut. By investing in a money market fund directly, you cut out the middleman, which is why MMFs often pay a little more than a bank will.
Also, when the Bank of England hikes interest rates, short-term MMFs react quickly. Banks, on the other hand, tend to drag their feet.
That’s because MMFs are influenced by short-term rates like SONIA (Sterling Overnight Index Average) – basically, the interest rate set by the Bank of England every night. This is usually higher than what you'll get from your bank.
And on the other hand, when rates fall, MMFs can take a bit longer to adjust. This is because they have to wait for their existing higher-yielding investments to mature before they can reinvest at the new, lower rates.
Money market funds are also highly liquid, meaning you can typically access your money quickly when you need it (usually within a few business days). This is a big advantage over fixed-term savings accounts, which may lock your money up for months or even years.
MMFs can be held within tax-advantaged wrappers like ISAs and SIPPs, which means your returns could be tax-free or tax-deferred, depending on the type of account.
MMFs, ISAs and savings accounts compared
| Feature | Money Market Funds | Savings accounts | ISAs |
|---|---|---|---|
| Risk | Low, but not risk-free. Can lose value in rare cases. | Very low risk (FSCS-protected). | Low risk, but depends on the type of ISA (cash vs stocks and shares). |
| Returns | Typically higher than savings accounts, but modest. | Usually lower than MMFs. | Can offer tax-free interest or returns, often similar to savings accounts. |
| Liquidity | Highly liquid (can access funds quickly). | Depends on the type (some may lock in funds). | Depends on the type (some may lock in funds). |
| Tax benefits | If held inside SIPP or ISA. | Interest is taxable above the personal savings allowance (unless using a Cash ISA). | Tax-free interest or returns in a Cash ISA or Stocks and Shares ISA. |
| Protection | Not protected by the FSCS. | FSCS-protected up to £85,000. | FSCS-protected for Cash ISAs, no protection for Stocks & Shares ISAs. |
| Best for | Short-term parking of cash with slightly better returns. | Low-risk savings with FSCS protection. | Tax-efficient saving and investing, depending on type. |
When should you use one?
Some people use MMFs as a short-term home for spare cash while they decide what to do with it next. Others might stash money here while saving for a wedding or a house deposit. They're also handy for people near or in retirement who want to keep their savings relatively safe while still getting a slightly better return than the bank.
They can also be used to diversify a portfolio, providing a liquid lump sum of cash that can be accessed if needed to pay off loans or cover emergencies.
The risks
While money market funds are more like savings accounts than stock market investments, they aren't risk-free. All investments have risk.
As we've covered, unlike money in a bank account, cash in a money market fund isn't protected by the FSCS. So if the fund collapses, you're not getting automatic government protection.
And while it's rare, these investments can lose value.
Just look at 2008, when the Reserve Primary Fund in the US "broke the buck", meaning its stable $1 per unit price dropped below $1 during the financial crisis. People rushed to pull their money out, but the fund couldn't meet all the withdrawals, so it had to suspend operations and liquidate.
Fast forward to 2020, and the Financial Conduct Authority (FCA) flagged another issue: liquidity.
At the start of the Covid pandemic, investors panicked and scrambled to withdraw their cash, putting severe strain on MMFs. Think the bank run on Bailey Brothers’ Building and loan, but with more online sell orders and fewer inspiring speeches.
Because of this, the FCA is now looking at tightening regulation. They're considering rules to increase the proportion of highly liquid assets these funds hold, making them more resilient during financial crises.
So, while it's unlikely, it's worth knowing that these products can, in rare cases, drop in value. This is something that won't happen with a standard savings account.
How do you invest in money market funds?
Now that you know what MMFs do, why people invest in them, and what the risks are, let's look at how you actually invest into one.
Step one: choose your fund
There are plenty of options to choose from, but here are four popular options available to UK investors, along with their respective OCFs – the annual fee charged by the fund provider:
- Amundi Smart Overnight Return (OCF 0.05%)
- BlackRock ICS Sterling Liquidity Fund (OCF 0.1%)
- Vanguard Sterling Short-Term Money Market Fund (OCF 0.12%)
- Royal London Short-Term Money Market (OCF 0.1%)
These are examples, not investment recommendations. Capital is always at risk when using investment products.
These funds primarily invest in short-term, high-quality debt from governments and top-rated companies, making them a safe place to park cash while earning a modest return.
When you’re browsing funds, you'll see key information about what the fund aims to achieve, along with the OCF/TER. Here's an example from InvestEngine:
With many funds, you can also choose whether you want the interest to be paid out to you (income class) or reinvested to boost the value of your investment (accumulation class).
Step two: decide how to hold your investment
You can buy MMFs through a General Investment Account (GIA), a Stocks & Shares ISA, or a SIPP (Self-Invested Personal Pension).
- A GIA has no tax benefits, meaning any interest or gains may be subject to capital gains tax and income tax.
- A stocks & Shares ISA allows you to earn tax-free interest and gains, but you can only deposit up to £20,000 per tax year.
- A SIPP (Self-Invested Personal Pension) gives you tax relief on contributions, meaning the government effectively boosts your investment. However, your money is locked away until at least age 55 (rising to 57 in 2028).
Step three: choose who to invest with
Once you've decided which fund to invest in, you'll need to choose which provider to invest with. Here are some factors to consider across popular brokers:
- Hargreaves Lansdown offers a great range of MMFs, so if you want lots of choices, it’s a solid pick. However, be aware that it comes with higher fees than some, including a 0.45% annual charge
- Vanguard charges a 0.15% annual fee (capped at £375), and you'll be limited to the Vanguard Sterling Short-Term Money Market Fund
- InvestEngine is a good choice if you’re all about cutting costs. There’s no platform fee, which is fantastic for DIY investors. They currently offer a choice of two MMFs: Amundi Smart Overnight Return and XTrackers GBP Overnight Rate Swap
- Trading 212 is great for beginners and those who want to keep things simple. There are no platform fees or dealing fees, making it a very cost-effective option. However, they also don’t offer a huge selection of MMFs, so it’s best suited for those who want to keep things low-cost and are okay with a more limited fund range.
Check out our beginner tutorial on investing in money market funds on Trading 212.
Step four: keep an eye on your investment
Once your money is working for you, don’t just forget about it – check in now and then to make sure it’s still on track.
While money market funds tend to be pretty steady, it’s always a good idea to stay in the loop. Platforms often provide easy tools to monitor performance, so you’ll know if there’s a shift in interest rates, fees, or returns.
Plus, if you’re saving for a short-term goal like a holiday or a big purchase, you’ll want to make sure your investment is keeping pace with your plans.
Bottom line
Money market funds can be a smart place to park your cash, offering better returns than most easy-access savings accounts, without locking your money away.
They’re low-risk, highly liquid, and can be held in ISAs or SIPPs for tax perks.
But don’t mistake them for savings accounts: they’re investments, not FSCS-protected deposits, and rare shocks can cause them to dip in value. Still, for short-term goals or a low-volatility buffer in your portfolio, MMFs offer a neat blend of safety, flexibility and (slightly) stronger returns.
Before you choose, though, be sure to shop around. Different platforms offer varying fees, fund selections, and features, so it’s worth comparing to find the best fit for your needs.
Financial Interest provides guidance, not advice. If you’re unsure about anything, speak with a qualified adviser. When investing, your capital is always at risk. Past performance does not guarantee future results.
