What's an ISA and how does it work?

What’s an ISA and how does it work?

[17 September 2025]
ISAs are a flexible and tax-efficient way to invest for your future, but it’s important to make the most of the opportunity.

Since their introduction in 1999, ISAs (or Individual Savings Accounts) have become one of the most popular ways to save and invest for the future, providing a simple and flexible way to help achieve financial freedom and peace of mind.

The key attraction of ISAs is that there is no liability to Income Tax or Capital Gains Tax on profits or withdrawals. Sheltering your money from tax can make a big difference to wealth you can create over the longer term.

But to ensure you’re making the most of the tax benefits on offer, it’s important to understand the different types of ISAs and how they work.

The value of an ISA with St. James’s Place will be directly linked to the performance of the funds selected and may fall as well as rise. You may get back less than you invested.

The favourable tax treatment of ISAs may be subjected to changes in legislation in the future.

Types of ISAs

The two most popular types of ISAs are:

1. Cash ISA
2. Stocks and Shares ISA

You can invest up to your annual allowance of £20,000 in this tax year, which can be split across different types of ISAs. But you cannot carry forward your allowance to the next tax year. If you don’t use it, you lose it.

You may also have the opportunity to pay into a Junior ISA – a great way to provide a solid financial foundation for your children and contribute to their long-term financial security. Find out more about JISAs here.

A Cash ISA

A Cash ISA is essentially the same as a regular savings account with a bank or building society, but there is no tax to pay on interest earned on the account. Although it doesn’t involve the risks of investing in stocks and shares, the downside of holding a Cash ISA is that the returns you receive may not necessarily keep pace with inflation, meaning your spending power is reduced. Over the longer term, a Cash ISA is therefore unlikely to make the most of the tax-saving benefits on offer.

Anyone can open a Cash ISA providing they’re aged 18 or over and are a UK resident for tax purposes. You can only open one Cash ISA in each tax year, but it is possible to transfer to another Cash ISA or a Stocks and Shares ISA with a different provider.

Cash ISAs are available as instant access accounts or fixed-term deposits, so they can be very flexible. But it’s worth considering that the personal savings allowance already lets basic-rate taxpayers earn up to £1,000 in interest each year from standard cash accounts, without paying tax on it. The allowance is £500 for higher-rate taxpayers and additional-rate taxpayers have no allowance.

Savers should therefore weigh up the benefits of holding their ISA allowance in cash versus investing it to potentially achieve better returns over the long term.

Please note that St. James’s Place does not offer a Cash ISA.

Stocks and Shares ISAs

A Stocks and Shares ISA offers the potential to achieve attractive long-term returns by investing your money into company shares, government or corporate bonds, property or other assets. But as with all investments, there is a risk to your capital and that the value of your ISA may fall.

To be eligible, you must be aged 18 or over and be a UK resident for tax purposes.

In just the same way as a Cash ISA, any profits earned from a Stocks and Shares ISA will be free of any further liability to Income Tax and Capital Gains Tax.

Stocks and Shares ISA are commonly invested in a portfolio of funds, rather than individual shares. This spreads your money far more widely, offering the benefits of diversification and professional management. By investing in assets capable of generating income and capital growth, a Stocks and Shares ISA gives you the chance to make the most of the long-term tax benefits of your annual ISA allowance.

In order to maximise the potential returns from a Stocks and Shares ISA, you must consider it as a medium to long-term commitment. It should be money that you can afford to tie up for at least five years, preferably longer. However, in the event that you do need to access your money, you are able to make a withdrawal at any time.

Our expert Advisers will steer you through the decision-making process and offer guidance on the most suitable solutions. We’re here to provide the peace of mind you need to ensure you’re making the right financial decisions for your future.

For further advice on ISAs and how to make sound financial investments, get in touch with Pinnacle Wealth Management and our Advisers will be happy to help.

The value of an ISA with St. James’s Place will be directly linked to the performance of the funds selected and may fall as well as rise. You may get back less than you invested.

An investment in a Stocks and Shares ISA will not provide the same security of capital associated with a Cash ISA.

The favourable tax treatment of ISAs may not be maintained in the future and is subject to changes in legislation.

SJP Approved 17/09/2025

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