Cash ISA comparison · UK rates
Illustrative comparison data — not personal financial advice. Verify rates on the provider’s own pages before acting.
Every UK taxpayer gets a £20,000 ISA allowance each tax year. Cash held inside a Cash ISA earns interest tax-free — no Personal Savings Allowance to worry about, no tax return entries. All providers in this table sit at FCA/PRA-authorised banks where FSCS deposit cover is £120,000 per eligible person per authorised firm (raised from £85,000 on 1 December 2025). Challenger providers that route deposits through partner banks qualify per partner bank, not per app.
Several challengers advertise a 12-month promotional rate that drops sharply to the standard rate once the bonus period expires. The table surfaces both where relevant so you can compare on the standard rate that would apply after the promo period — assuming rates hold. To move an existing Cash ISA to a higher-rate provider without losing your tax-free status, see the how to switch guide.
As of August 2026, the highest-rate Cash ISA among the 18 providers Feefee tracks is Atom at 4.25% AER. Ranked mechanically by headline rate — illustrative comparison, not advice.
| Provider | Rate (AER) | Promo / Standard | Last verified | Source |
|---|---|---|---|---|
| #1Atom | 4.25% AER | Standard only | 18 Aug 2026 | Source → |
| #2Charter | 4.23% AER | Standard only | 18 Aug 2026 | Source → |
| #3Aldermore | 4.20% AER | Standard only | 18 Aug 2026 | Source → |
| Cynergy | 4.15% AER | Standard only | 18 Aug 2026 | Source → |
| Chip | 3.75% AER | 3.81% AER/3.55% AER | 18 Aug 2026 | Source → |
| Tandem | 3.75% AER | Standard only | 18 Aug 2026 | Source → |
| Trading 212 | 3.60% AER | 4.51% AER/3.60% AER | 18 Aug 2026 | Source → |
| Nationwide | 3.30% AER | Standard only | 18 Aug 2026 | Source → |
| Zopa | 3.25% AER | Standard only | 18 Aug 2026 | Source → |
| OakNorth | 2.75% AER | Standard only | 19 Aug 2026 | Source → |
| Plum | 2.54% AER | 4.31% AER/2.54% AER | 18 Aug 2026 | Source → |
| HSBC UK (savings) | 2.50% AER | Standard only | 18 Aug 2026 | Source → |
| Santander | 2.00% AER | Standard only | 18 Aug 2026 | Source → |
| Coventry BS | 2.00% AER | Standard only | 19 Aug 2026 | Source → |
| NatWest (savings) | 1.15% AER | Standard only | 18 Aug 2026 | Source → |
| Halifax (savings) | 1.05% AER | Standard only | 2 May 2026 | Source → |
| Barclays (savings) | 1.00% AER | Standard only | 2 May 2026 | Source → |
| Lloyds savings | 0.75% AER | Standard only | 2 May 2026 | Source → |
Methodology & caveats
- FSCS per banking licence. The £120,000 FSCS deposit limit applies per authorised bank, not per app. Challenger providers (Trading 212, Chip, Plum) route Cash ISA deposits through partner banks — your protection depends on which bank holds your funds and whether you also hold deposits directly with that bank.
- Promo vs standard rates. Promotional rates are typically available to new customers only and revert after 12 months. The “Rate (AER)” column shows the current headline (promo for providers that offer one); “Promo / Standard” shows both figures where they differ.
- Sources. Every figure is sourced from the provider’s own page — see /sources for every source URL and last-checked date, and /comparison for the complete multi-product rate table.
- Not advice. This is illustrative comparison data — not personal financial advice or a recommendation. Rates change between Feefee’s verifications and yours; always confirm on the provider’s own page before opening or transferring an account.