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Matthew is an award-winning journalist, specialising in savings, tax and insurance.
There are just days left until the financial year ends and savers have a final chance to use up their £20,000 tax-free Isa allowance before it renews on 6 April.
With Isa season in full swing and providers boosting rates to attract new savers, now is the perfect time to open an account. But rushing for the top deal could mean missed opportunities or costly mistakes.
Here's our pick of the most common pitfalls to avoid when opening a cash Isas this spring.
The end of the financial year is a use-it-or-lose-it time for Isa savers. That's because the £20,000 tax-free limit resets every 12 months on 6 April and you can't carry any remaining allowance over to the next year.
You can, however, transfer the full balance of a previous year's Isa (including interest earned) or just a portion of it, without affecting your current year's allowance.
And don't forget that if you've used up your annual Isa allowance but your partner hasn't, you can pay into their account instead, effectively increasing your shared Isa allowance to £40,000. If you want to save for your child, you could also open a Junior Isa on their behalf. Junior Isas have an annual allowance of £9,000.
It means a family of four has a combined annual tax-free allowance of £58,000.
The average top-10 instant-access cash Isa rate on 26 March 2026 was 4.3% AER, according to Moneyfacts data. But seven out of 10 of the market-leading deals have catches.
For example, headline rates may include short-term bonuses. Plum's instant-access cash Isa pays the top rate of 4.66% AER, but that includes a 2.12% boost that expires after 12 months, leaving you with a much lower 2.54% thereafter.
Other accounts restrict the number of withdrawals you can make. Moneybox, for instance, offers a top rate of 4.26% AER for its instant-access cash Isa. However, savers can withdraw money from the account only three times per year before interest drops to 3.45%.
Fixed-term cash Isas may guarantee you the same rate for the entire term, but savers need to act swiftly when the account is due to mature.
Take another look at the T&Cs, because if you don’t give your bank instructions about what to do next with your savings pot, your provider may roll your money into a lower-rate deal or dump it into a current account earning next to nothing.
It's true that rates get a boost in February and March, but there is a second 'Isa season' to watch out for.
The start of the new tax year on 6 April is when the tax-free allowance renews, and many providers hike interest rates on cash Isa products to entice savers.
If you have the funds to do so, consider maxing out your £20,000 allowance at the beginning of the financial year. Not only does investing earlier remove some of the pressure to make a hasty decision at the end of the tax year, but it also means your cash will be put to work for longer.
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Instant-access and shorter-term Isas currently offer better returns, but don't just look at the rate when choosing an account.
Remember, instant-access accounts have variable rates. This means that providers can cut the interest offered on these deals whenever they like, so your money might not grow at that pace for long.
Locking your money away in a longer-term fixed Isa guarantees you the same rate for years to come, regardless of what's going on in the rest of the market. Fixing could also protect your cash from major changes coming up next year.
If you've got savings you won't need for at least five years, you could earn a better return by investing instead. A stocks and shares Isa means all profits and dividends are tax-free.
New rules that came into effect on 6 April 2024 mean it's now easier than ever to switch between providers and get the best deal.
You can now open and pay into more than one cash Isa in the same tax year. Previously, you were limited to paying into just one of each Isa type per year.
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