Why putting your money in a cash ISA will make you poorer

Using a cash ISA might seem sensible but it will end up costing you money. Here’s why…

The content of this article was relevant at the time of publishing. Circumstances change continuously and caution should therefore be exercised when relying upon any content contained within this article.

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More.

Generally speaking, cash ISAs are a great product. Cash ISAs allow you to save money without interest received being liable for tax. This is especially attractive for higher-rate taxpayers who have to pay out on savings interest over £500 a year. And if you’re an additional rate (45%) taxpayer, using a tax efficient wrapper like a cash ISA is essential because there’s no savings allowance at all for taxpayers who fall into this bracket.

However, despite the tax benefits of cash ISAs, they have one fundamental flaw. If you’re using a cash ISA today, rather than growing your wealth, your money is losing value.

Wealth destroying 

According to analysis by Moneyfacts, 2017 was the worst year on record for cash ISA returns. The average instant access account offered just 0.93% interest on balances.

The problem is that this stingy level of interest isn’t enough to protect your portfolio from the scourge of inflation. Last year, the Consumer Price Index — the most widely used measure of inflation in the UK — averaged 2.6%, so the average cash ISA saver saw the value of savings eroded by 1.67% in real terms for the full year.

The long-term figures are even more depressing. According to my calculations, over the past 10 years to keep pace with inflation, your savings would have had to have been growing at a rate of 2.9% per annum. As the average Bank of England base rate between 2008 and 2017 was only 0.5%, savers have been left short-changed.

If cash ISAs are such a bad investment then, where should you be looking to get the best return on your money?

Other options 

Well, one solution is to use low-cost funds to invest in the stock market. Over the past 10 years, the FTSE 100 — the UK’s leading stock index — has produced an average return around 8% per annum for investors, easily outperforming inflation and more.

However, if you’re not comfortable investing in shares and would rather put your money to work in a way that comes with less risk, but still manages to nullify the negative impact of inflation, a good option is to use a low-cost bond fund.

Bonds have similar qualities to cash. They generally come with significantly less risk than investing in equities, primarily because the price of bonds doesn’t vary significantly day to day. What’s more, bonds come with a guaranteed level of income which, unlike equity dividends, cannot be cut whenever the company feels like it.

Bond funds 

Bond funds provide diversification across many different bond instruments at a low cost so all you need to do is sit back and relax. 

The returns for each bond fund vary, depending on the level of risk involved. High-grade corporate bond funds can add 5% per annum, while government bond funds yield less (although still more than the average cash ISA interest rate) but are considered to be more secure.

So, if you want to protect and grow the value of your money over the long-term, it makes sense to ditch your cash ISA today. As my figures above show, the stock market is a much better option. And if you don’t want to invest in shares, bonds are the next best thing.

Rupert Hargreaves owns no share mentioned. The Motley Fool UK has no position in any of the shares mentioned. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

More on Investing Articles

Thoughtful man using his phone while riding on a train and looking through the window
Investing Articles

Here’s how to try and create a £10,000 second income portfolio

Millions of UK investors use the Stocks and Shares ISA to build wealth and eventually take a second income. Dr…

Read more »

ISA Individual Savings Account
Investing Articles

3 steps to aim for a lifetime of passive income from a new ISA

It's that time of year again when we're all planning how make the most of our new ISA limit to…

Read more »

Three signposts pointing in different directions, with 'Buy' 'Sell' and 'Hold' on
Investing Articles

A once-in-a-decade chance to buy Nvidia shares at a discount?

Nvidia shares are trading at a discount to the S&P 500 for the first time in 10 years. Is it…

Read more »

Hand of person putting wood cube block with word VALUE on wooden table
Investing Articles

This FTSE 100 stock’s crashed over 25%. But could it be an amazing opportunity for income and growth?

There’s one FTSE 100 stock that’s been badly affected by the conflict in the Gulf region. But could this be…

Read more »

Man hanging in the balance over a log at seaside in Scotland
Investing Articles

How many Aviva shares must I buy to give up work and live off the income?

Aviva shares are on track to pay a 6.7% yield in 2026, generating a highly tempting stream of passive dividend…

Read more »

Typical street lined with terraced houses and parked cars
Investing Articles

£5,000 invested in Taylor Wimpey shares 5 years ago is now worth…

Taylor Wimpey shares haven’t been a terrific investment over the last five years, but has this share price weakness created…

Read more »

ISA coins
Investing Articles

Looking for dividend stocks for a new ISA? These 2 are among the most popular in 2026

Some investors worry about where share prices are going. Others just sit out volatility and rely on income from dividend…

Read more »

Young female analyst working at her desk in the office
Investing Articles

£500 invested in Legal & General shares 5 years ago is now worth…

Investors are rushing to buy Legal & General shares as the dividend yield hits 8.9%! But how much money are…

Read more »