XTB Flexible Cash ISA — earn up to 6% AER, tax-free
Tax-free interest on your savings, daily accrual, monthly payouts, and no account fees. Open before 30 April 2026 to lock in the 2% boost for the first 90 days — on top of the standard 4% AER variable rate.
Your capital is at risk. The value of your investments may go up or down. Tax treatment depends on your individual circumstances and ISA regulations which may change. T&Cs apply.
What is the XTB Flexible Cash ISA?
The XTB Flexible Cash ISA is a UK tax-free savings account that pays interest on your cash balance. Unlike a standard fixed-rate ISA, it's flexible — you can withdraw money and pay it back within the same tax year without reducing your annual £20,000 allowance. All interest earned is free of UK income tax.
At a glance
| Parameter | Value |
|---|---|
| Rate (new clients) | 6.00% AER * |
| Rate (standard) | 4.00% AER |
| ISA type | Flexible Cash ISA |
| Account fees | £0 |
| Minimum deposit | £0 |
| Withdrawal limit | None |
| Interest calculated | Daily |
| Interest paid | Monthly |
| Annual ISA allowance | £20,000 (2025/26) |
| Protection | FSCS up to £120,000 |
* 6.00% AER = 4.00% standard variable + 2.00% boost for 90 days from the ISA open date. New clients only, ISA opened between 1 March and 30 April 2026.
How the 6% AER works
The 6% headline rate is variable and is split into two parts:
- 4% AER standard rate — the base variable rate XTB pays on your Cash ISA. It tracks the Bank of England base rate and XTB's banking partners, and can be adjusted weekly.
- + 2% AER boost — a promotional boost paid for 90 days from the day you open the ISA. Available to new XTB clients only.
After the 90-day boost ends, you continue earning the standard variable rate (currently 4%) for as long as you hold the ISA. Interest accrues daily on your closing balance and is paid into your ISA monthly.
How XTB compares to other UK Cash ISAs
| Provider | Rate (AER) | Type | Min deposit | Fees |
|---|---|---|---|---|
| XTB | 6.00% | Flexible | £0 | £0 |
| Trading 212 | 4.40% | Flexible | £1 | £0 |
| Plum | 4.32% | Fixed | £1 | £0 |
| eToro | 4.47% | Flexible | £500 | £0 |
| MoneyBox | 4.32% | Fixed | £500 | £0 |
Rate footnotes — XTB: 4% variable + 2% boost for 90 days (new clients, opened by 30 Apr 2026). Trading 212: 3.60% variable + 0.80% bonus for 12 months (new customers, no bonus on prior-year transfers). Plum: 2.54% variable + 1.76% bonus for 12 months (new clients only, no bonus on transfers-in). eToro: Via Moneyfarm partnership. Keep min £500 balance and ≤3 withdrawals/year, paid after 12 months. Intro year: 3.67% AER. MoneyBox: Includes 0.87% variable 12-month bonus. Drops to 0.75% if you make more than 3 withdrawals in a year. All rates are advertised headline AERs and are variable unless stated; always verify on the provider's website before applying.
Flexibility — what it really means
Most fixed-rate Cash ISAs lock you in: withdraw before the term ends and you typically lose the boosted rate or pay an interest penalty. A Flexible Cash ISA works differently:
- Withdraw any amount whenever you want.
- If you pay the money back within the same tax year (ends 5 April), it doesn't count against your £20,000 annual allowance.
- You keep earning interest on the balance that's in the account.
This is useful if you want to park an emergency fund in an ISA without losing access to it.
Key ISA rules for 2025/26
- Annual allowance: £20,000 across all your ISAs (Cash, Stocks & Shares, Innovative Finance, Lifetime).
- Tax-free: interest earned inside the ISA is free of UK income tax.
- You can hold multiple Cash ISAs in the same tax year since April 2024, as long as you don't exceed the £20,000 total.
- Transfers: existing Cash ISAs can be transferred to XTB without using your current-year allowance.
Eligibility
- UK tax resident aged 18+.
- Not a US Person (US citizens, green-card holders and US taxpayers are excluded).
- For the 6% AER — you must be a new XTB client opening your first XTB account, and the ISA must be opened between 1 March and 30 April 2026.
Protection
XTB Ltd. is authorised and regulated by the UK Financial Conduct Authority (FCA Register No. 522157). Cash ISA client money is held in segregated Tier 1 UK banks under FCA CASS rules, with FSCS protection up to £120,000 per client in the unlikely event of XTB insolvency.
Frequently asked questions
What is a Flexible Cash ISA?
A Flexible Cash ISA is a tax-free savings account that lets you withdraw money and replace it within the same tax year without reducing your £20,000 ISA allowance. Interest earned is free of UK income tax, and XTB pays it daily.
Who qualifies for the 6% AER rate?
The 6% AER applies only to new UK clients who open either a Cash ISA or a Stocks & Shares ISA between 1 March and 30 April 2026. The rate is 4% variable + a 2% boost for 90 days from the ISA open date. After 90 days, it reverts to the standard 4% AER (also variable). Existing clients receive 4% AER.
Is my money protected?
Yes. XTB holds all Cash ISA client money in segregated Tier 1 UK banks under FCA CASS rules. In the unlikely event of XTB insolvency, your balance is covered by the FSCS up to £120,000 per client.
How much can I pay in?
Up to £20,000 in the 2025/26 tax year — this is the total ISA allowance shared across all your ISAs (Cash, Stocks & Shares, Innovative Finance, Lifetime).
How does the 90-day boost actually work?
From the day you open your XTB ISA, you earn 4% (the standard rate) plus a 2% boost for 90 calendar days. On day 91, the boost ends and you continue earning the standard variable rate (currently 4%, subject to Bank of England rate changes).
Can I transfer an existing ISA to XTB?
Yes. Cash ISA transfers are supported. The 6% rate applies to new XTB clients, so a transfer counts toward the boosted rate as long as you were not a prior XTB client.
Open your Cash ISA before 30 April
The 2% boost is only available to new clients who open an ISA in the promotional window. After that, you're on the standard 4% variable rate.
Open an XTB Cash ISAYour capital is at risk. The value of your investments may go up or down. Tax treatment depends on your individual circumstances and ISA regulations which may change. T&Cs apply.