Cash ISA

Harpenden Building Society Online Single Access ISA Review

One of the best-paying instant access cash ISAs, from Harpenden Building Society. It ranks 19th of 115 instant access cash ISAs we track.

Variable rate

4.06%AER

Rate checked Oct 2026Got this account? Leave a review

Protection

FSCS£120,000

Min balance

£1

Max balance

£250,000

Access

1 withdrawal, Else rate drops to 1.35%

Interest paid

Annually

Transfers in

Accepted

Rate Tiers

1 or fewer withdrawals/year

4.06%AER

Higher rate applied on 31 Dec if condition met

2 or more withdrawals/year

1.35%AER

Lower rate applies if condition not met

How It Stacks Up

Ranks 19th of 115

Instant access cash ISAs we track

Among the best
This account 4.06%
UK CPI (Aug 2026)
3.10%
Pays 0.96% more
Average instant access cash ISA
2.91%
Pays 1.15% more
Best instant access cash ISA
4.87%
Pays 0.81% less

Inflation: ONS. Averages and best rates: accounts on DepositScout.

A better-paying alternative

Trading 212 bank logo

Trading 212

Cash ISA

4.75%

AER

  • Pays 0.69% more than this Harpenden Building Society account
  • Includes a 1.15% bonus for 12 months, then 3.60%
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Pros and cons

  • Pro: New and existing savers
  • Con: The rate is variable, so it can go down

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Estimated returns with Harpenden Building Society's Cash ISA

What you could earn with Harpenden Building Society's Online Single Access ISA.

Estimated interest

£1,000 saved

£40.60

At 4.06% AER

£5,000 saved

£203

At 4.06% AER

£10,000 saved

£406

At 4.06% AER

£250,000 saved

£10,150

At 4.06% AER

Estimated over one year, if the rate stays the same and interest is left in. Amounts outside the account's minimum or maximum aren't shown.

Our Expert Opinion on Harpenden Building Society Online Single Access ISA

Jonny PeaseCo-Founder, DepositScout

Harpenden's Online Single Access ISA pays 4.06%, which is 1.19% behind the cash ISA market leader at 5.25% and sits below the market average, so it is hard to get excited about the headline rate. The real catch is the name: make two or more withdrawals in a year and your rate collapses to 1.35%, with the higher rate only confirmed on 31 December. It does beat August 2026 CPI of 3.1% by 0.96%, and Hampshire Trust Bank's Easy Access Online ISA matches 4.06% with fewer withdrawal strings attached.

Compare Cash ISAs

2 alternatives to Harpenden Building Society's Online Single Access ISA

Same type of account, closest on rate.

Common questions about the Online Single Access ISA

D

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