What an ISA savings account is and how the tax break works

An ISA (Individual Savings Account) is a savings account where the interest you earn is not taxed by HMRC. Money you put in grows without any tax bill at the end of the year, no matter how much interest accumulates. You do not report ISA interest on a tax return, and you do not owe tax on it — the account itself handles the tax exemption.

This is different from a regular savings account, where interest above your personal savings allowance gets taxed at your marginal rate (20%, 40%, or 45% depending on your income). An ISA removes that tax entirely. The trade-off is that you can only pay in a limited amount each tax year, and the money must stay in the account type you choose.

ISAs have been available since 1999 and are run by banks, building societies, and other financial institutions. They are not government bonds or investment products — they are ordinary savings accounts with a tax wrapper around them.

Key Takeaways

  • Interest earned in an ISA is not taxed, so you keep all the interest your money makes without filing a tax return for it.
  • You can pay in up to £20,000 per tax year across all your ISAs combined, though you can only pay into one Cash ISA per year.
  • The four types of ISA — Cash, Stocks and Shares, Innovative Finance, and Lifetime — have different rules about what you can hold and how much you can earn.
  • Money in an ISA stays in that account type; you cannot move Cash ISA funds into a Stocks and Shares ISA without closing the account or using a transfer process.
  • If you stop using an ISA or close it, the tax exemption ends, and any interest earned after closure is taxed like a regular account.

The four types of ISA and what each one holds

A Cash ISA works like a regular savings account but with no tax on interest. You deposit money, it earns interest at a rate set by the bank, and that interest is never taxed. Cash ISAs are the most common type and suit people who want a straightforward place to keep savings. Interest rates vary by provider and account tier, just as they do for regular savings accounts.

A Stocks and Shares ISA lets you invest in stocks, bonds, funds, and other securities without paying tax on dividends or capital gains. If you buy shares worth £5,000 and they grow to £7,000, you owe no tax on that £2,000 gain. You manage the investments yourself or choose a managed fund, and the tax exemption applies to all growth and income. This type carries investment risk — your money can go down as well as up.

An Innovative Finance ISA (also called a Peer-to-Peer ISA) lets you lend money through peer-to-peer platforms and earn interest tax-free. You are lending to individuals or small businesses through a regulated platform, and the interest you receive is not taxed. This type also carries risk because the borrower might default.

A Lifetime ISA is designed for people aged 18 to 39 who are saving for a first home or retirement. You can pay in up to £4,000 per year, and the government adds a 25% bonus (up to £1,000 per year). The bonus and all growth are tax-free. You can withdraw money penalty-free only for a first home purchase or after age 60; early withdrawal for other reasons incurs a 25% penalty on the bonus.

Annual limits and how the £20,000 allowance works

You can pay a total of £20,000 per tax year (6 April to 5 April) across all your ISAs combined. This is a single allowance that covers Cash ISAs, Stocks and Shares ISAs, Innovative Finance ISAs, and Lifetime ISAs together. If you pay £8,000 into a Cash ISA, you have £12,000 left to use in other ISA types that year.

The Lifetime ISA has its own separate rule: you can pay in up to £4,000 per year into a Lifetime ISA, and this counts toward your £20,000 overall limit. So if you pay £4,000 into a Lifetime ISA, you have £16,000 left for other ISAs.

You can only pay into one Cash ISA per tax year, but you can pay into a Cash ISA and a Stocks and Shares ISA and an Innovative Finance ISA in the same year, as long as the total does not exceed £20,000. If you want to switch your Cash ISA to a different provider, you use a transfer process rather than opening a second Cash ISA.

Unused allowance does not roll over. If you pay in £15,000 in one tax year, the remaining £5,000 is lost when the tax year ends on 5 April.

How interest and growth are taxed (or not taxed) in an ISA

Interest earned in a Cash ISA is completely tax-free. If your Cash ISA earns £500 in interest over a year, you owe no tax on it and do not report it to HMRC. The bank or building society does not send you a tax form for ISA interest because there is no tax to report.

In a Stocks and Shares ISA, dividends paid by companies and capital gains from selling shares or funds are both tax-free. If you own a fund that pays £200 in dividends, or you sell shares for a £1,000 profit, neither is taxed. This is the main advantage of a Stocks and Shares ISA over a regular investment account, where dividend tax and capital gains tax would apply.

In an Innovative Finance ISA, the interest you receive from lending is tax-free. If you lend £10,000 through a peer-to-peer platform and earn £400 in interest, that £400 is not taxed.

In a Lifetime ISA, the government bonus and all growth are tax-free. The 25% bonus is added by the government and is not taxed. Any interest or investment growth inside the account is also tax-free.

Opening an ISA and moving money between accounts

To open an ISA, you contact a bank, building society, or investment platform that offers ISAs. You provide proof of identity and address, just as you would for any savings account. The process usually takes a few days to a week. You can open an ISA online, by phone, or in person at a branch, depending on the provider.

Once your ISA is open, you can pay money in by bank transfer, standing order, or direct debit. Some providers also accept cash deposits at branches. There is no minimum or maximum deposit per transaction — you simply cannot exceed your annual £20,000 allowance.

If you want to move money from one ISA to another — for example, from a Cash ISA at one bank to a Cash ISA at another bank — you use a transfer process. You ask the new provider to transfer your balance from the old provider. The old provider sends the money directly to the new one, and the tax exemption continues unbroken. This does not count as a new payment into your allowance; it is a transfer of existing ISA money.

You cannot simply withdraw money from one ISA and pay it into another ISA in the same tax year without using the transfer process, because that would count as a new payment and could breach your allowance or the one-Cash-ISA-per-year rule. Always ask the new provider to handle the transfer for you.

What happens if you close an ISA or stop using it

If you close an ISA, the tax exemption ends immediately. Any interest earned after the account closes is treated as interest on a regular savings account and is subject to tax in the normal way. If you close a Stocks and Shares ISA, future gains are subject to capital gains tax.

If you simply stop paying money into an ISA but leave it open, the tax exemption continues. The money already in the account keeps growing tax-free. You can reopen payments into the same ISA in a future tax year without losing the exemption on the existing balance.

If you move abroad, you can no longer pay into an ISA, but money already in the account continues to grow tax-free as long as you remain the registered account holder. Some providers may close your account if you become a non-resident, so check your provider's terms.

ISA interest rates and how they compare to regular savings accounts

ISA interest rates are set by individual providers and vary widely. Some Cash ISAs offer competitive rates close to the best regular savings accounts; others offer much lower rates. The tax-free status does not mean the interest rate is higher — it means you keep all the interest you earn, rather than paying tax on it.

To decide whether an ISA makes sense for you, compare the ISA rate to the regular savings rate at the same provider, then calculate how much tax you would owe on the regular account. If you are a basic-rate taxpayer (20% tax), you would owe 20% tax on interest above your personal savings allowance in a regular account. If you are a higher-rate taxpayer (40%), you owe 40% tax. An ISA eliminates that tax entirely.

For example, if a Cash ISA pays 4% and a regular savings account at the same bank pays 4.2%, the ISA might still be better if you are a higher-rate taxpayer, because the tax on the regular account would reduce your net return below 4%. Use a tax calculator or ask your provider to compare the net return after tax.

Frequently Asked Questions

Can I have more than one ISA at the same time?

Yes, you can hold multiple ISAs as long as you follow the rules. You can have one Cash ISA, one Stocks and Shares ISA, one Innovative Finance ISA, and one Lifetime ISA open at the same time. You can only pay into one Cash ISA per tax year, but you can pay into the others simultaneously. The total across all types cannot exceed £20,000 per year.

What happens to my ISA if I die?

Your ISA ceases to be an ISA when you die, and the tax exemption ends. The money becomes part of your estate and is handled according to your will or the rules of intestacy. Any interest earned after your death is subject to tax. Your executor or administrator should notify the ISA provider of your death.

Can I withdraw money from my ISA whenever I want?

Yes, Cash ISAs and Stocks and Shares ISAs have no withdrawal restrictions — you can take money out at any time, subject to the provider's terms. Innovative Finance ISAs depend on the platform; some allow withdrawals, others do not until loans are repaid. Lifetime ISAs penalise withdrawals for reasons other than a first home purchase or age 60, with a 25% penalty on the government bonus.

Do I need to report my ISA on my tax return?

No. ISA interest and growth are not reported to HMRC and do not appear on your tax return. The tax exemption is automatic and built into the account. You do not need to tell HMRC you have an ISA.

Can I transfer an ISA to someone else?

No, an ISA is personal to you and cannot be transferred to another person while you are alive. After your death, the money passes to your estate but loses its ISA status. Each person must open their own ISA in their own name.