ISA Switch Calculator
Moving to a better ISA rate is not the risky decision it sometimes feels like — done correctly, switching provider does not cost you any tax-free status or count against your annual allowance. This calculator projects your existing ISA against a new rate over your chosen term, so you can see whether the improvement is actually worth the effort of moving.
ISA Switch Calculator
See how much more interest you could earn by switching to a better-rate ISA.
The One Mistake That Loses Your Tax-Free Status
This is the single most important thing to know before switching: withdrawing money from an ISA yourself and paying it into a new one is not the same as transferring it, and doing it that way genuinely loses tax-free protection on that money. A withdrawal followed by a fresh deposit counts as new money against your current year’s £20,000 allowance, not a preserved transfer of money that was already sheltered in previous years. The correct process is always to use your new provider’s official ISA transfer service, instructing them to request the funds directly from your old provider — never withdrawing the money into your own bank account as a middle step.
This mistake is more common than it might seem, since closing an old account and opening a new one feels like the natural, obvious way to switch anything else — a bank account, a mobile contract — but ISAs specifically require this different, formal transfer process to preserve the tax-free status built up in previous years.
How a Proper Transfer Actually Works
Once you start an official transfer with your new provider, they contact your existing provider directly and arrange the move on your behalf — you never handle the money personally at any point in the process. Cash ISA transfers are generally required to complete within 15 working days; transfers involving a Stocks and Shares ISA, particularly if investments need to be sold and repurchased, can take longer, sometimes several weeks. During this period your money remains fully protected and continues earning interest or growing, either under the old terms or the new ones, depending on your specific provider’s process.
It is worth starting the process by contacting the new provider first, not the old one — the receiving provider is generally responsible for coordinating the transfer, so beginning there rather than trying to arrange an exit with your current provider directly avoids unnecessary confusion about which side is meant to initiate it.
Old Money and New Money Follow Different Rules
Money paid into an ISA in previous tax years can be transferred in full or in part, entirely separately from your current year’s allowance — moving it does not use up any of this year’s £20,000 limit. Money paid in during the current tax year, however, generally has to be transferred in full if you want to move it at all; most providers will not let you split a current year’s contributions between two different ISA providers. This distinction is worth checking with both your old and new provider specifically if you have made contributions this tax year and are only planning to move part of your overall ISA balance.
A Small Rate Gap, Added Up Over Years
A £15,000 ISA balance growing at 2.8% for five years reaches roughly £17,220. The same balance moved to a provider offering 4.2% over the same five years reaches roughly £18,430 instead — an extra £1,205 purely from the rate difference, with the balance itself unchanged. On a smaller balance or a shorter term, the same percentage gap produces a proportionally smaller pound figure, which is exactly why checking the actual pounds involved, not just the percentage difference, matters before deciding whether a switch is worth the effort.
Is the Rate Gap Actually Worth the Hassle
A switch that looks meaningful on a headline rate can still be a fairly small amount in pounds over a short term, particularly on a modest balance — this calculator shows the actual extra interest in pounds over your chosen term, not just the percentage gap, since a 0.5% difference is a genuinely different decision on a £2,000 balance than on a £50,000 one. It is also worth checking whether your current provider’s rate is a temporary introductory rate about to drop, since that can make switching worthwhile even for a modest headline gap today. Our ISA Growth Calculator is useful if you are starting a new ISA from scratch rather than switching an existing one, and our Savings Interest Calculator is worth checking too if you are also comparing against a standard, non-ISA savings account.
Frequently Asked Questions
Does transferring my ISA affect my annual allowance?
No — a properly conducted transfer through your provider’s official process does not count against your current year’s £20,000 allowance, regardless of how much is being moved.
Can I transfer between different ISA types, like Cash to Stocks and Shares?
Yes — transfers between different ISA types are generally allowed, though moving into a Stocks and Shares ISA means the money then becomes exposed to investment risk, which is a genuinely different consideration from simply moving between two Cash ISAs.
Will I lose interest while the transfer is happening?
Reputable providers generally aim to avoid a gap where money earns no interest during a transfer, though the exact handling varies by provider, so it is worth asking directly how your specific transfer will be handled during the transition period.
Is there a limit to how many times I can transfer my ISA?
There is no limit on the number of transfers you can make, though each provider may have its own account opening and closing procedures, and multiple transfers in a short period is rarely necessary or beneficial beyond finding a genuinely better rate.
Does my new provider need to accept transfers in?
Yes — not every ISA product accepts transfers in, so it is worth confirming this specifically with your intended new provider before starting the process, since some accounts are designed only for new money rather than incoming transfers.
Is there a fee for transferring my ISA?
Some providers, particularly for Stocks and Shares ISAs, charge an exit fee for transferring out, so it is worth checking your current provider’s terms and factoring any fee into whether a switch is genuinely worthwhile overall.
Important Information
This calculator provides an estimate based on the figures you enter and does not constitute financial advice. Transfer timescales and rules can vary by provider and ISA type. For advice specific to your circumstances, consult a qualified financial adviser. See our Disclaimer for further information.