XTB Flexible Cash ISA — 4% AER, tax-free

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

* The 6.00% AER launch offer (4.00% standard variable + a 2.00% boost for 90 days from the ISA open date, new clients only) ran from 1 March to 30 April 2026 and is closed. Accounts opened today earn the standard 4.00% AER variable rate.

How the 6% AER worked

This promotion closed on 30 April 2026 and is kept here for reference. The 6% headline rate was variable and was 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 that was paid for 90 days from the day you opened the ISA. It was available to new XTB clients only and is no longer offered.

After the 90-day boost ended, the account reverted to the standard variable rate — currently 4% AER — 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

Rate footnotes — XTB: Standard variable rate. The 6% launch offer (4% + a 2% boost for 90 days, new clients) closed 30 April 2026. Trading 212: 3.60% variable + 0.80% introductory uplift for 12 months (new customers, no uplift on prior-year transfers). Plum: 2.54% variable + 1.76% introductory uplift for 12 months (new clients only, none 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 a 0.87% variable 12-month uplift. 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 2026/27

• 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 (closed) — you had to be a new XTB client opening your first XTB account, with the ISA 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