Money Market Funds vs a Cash ISA in 2026: Comparing Two 'Low-Risk' Homes for Savings
Money market funds and cash ISAs are both marketed as low-risk options for cash, but they sit in genuinely different regulatory and protection categories worth understanding before treating them as interchangeable.
Deposit vs Investment: The Core Distinction
| Cash ISA | Money Market Fund | |
|---|---|---|
| Structure | Cash deposit with bank/building society | Investment fund holding short-term debt instruments |
| Protection | FSCS deposit protection per institution | Investment protection rules, different basis |
| Value stability | Guaranteed nominal balance | Aims for stability, not guaranteed |
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Open ISA calculatorMoney Market Funds Within an ISA Wrapper
Money market funds can typically sit inside a stocks and shares ISA, bringing tax-efficient treatment of returns — but this is a different ISA type to a cash ISA, and the underlying fund still carries an investment risk profile even while wrapped for tax purposes.
Why Someone Might Choose a Money Market Fund
Some investors use money market funds to hold cash-like assets within a broader investment portfolio — for example, money not yet invested, or liquidity held alongside other investments on the same platform — rather than moving money between separate cash and investment accounts.
What to Check Before Choosing
- Confirm the exact protection basis — FSCS deposit protection vs investment protection rules.
- Understand that a money market fund is technically an investment, not a deposit, even if designed to behave with low volatility.
- Decide whether the goal is pure capital security or convenient liquidity within an investment platform.
- Check whether the fund sits inside a cash ISA or a stocks and shares ISA — they are not interchangeable wrappers.
- Compare rates and typical stability of both options directly before committing.
Frequently asked questions
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