Cash ISA

Harpenden Building Society Online ISA Review

A competitive instant access cash ISA from Harpenden Building Society. It ranks 48th of 115 instant access cash ISAs we track.

Variable rate

3.40%AER

Rate checked Oct 2026Got this account? Leave a review

Protection

FSCS£120,000

Min balance

£1

Max balance

£250,000

Access

Instant

Interest paid

Annually

Transfers in

Accepted

How It Stacks Up

Ranks 48th of 115

Instant access cash ISAs we track

Above average
This account 3.40%
UK CPI (Aug 2026)
3.10%
Pays 0.30% more
Average instant access cash ISA
2.91%
Pays 0.49% more
Best instant access cash ISA
4.87%
Pays 1.47% 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 1.35% more than this Harpenden Building Society account
  • Includes a 1.15% bonus for 12 months, then 3.60%
Compare Cash ISAs

We may earn a commission if you open this account.

A Good Fit For

  • Pro: New and existing savers
  • Pro: Savers who want instant access

Worth Weighing Up

  • Con: The rate is variable, so it can go down

Please verify all details with the provider – see our Disclaimer

See all Harpenden Building Society accounts

Estimated returns with Harpenden Building Society's Cash ISA

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

Estimated interest

£1,000 saved

£34.00

At 3.4% AER

£5,000 saved

£170

At 3.4% AER

£10,000 saved

£340

At 3.4% AER

£250,000 saved

£8,500

At 3.4% 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 ISA

Jonny PeaseCo-Founder, DepositScout

Harpenden Building Society's Online ISA pays 3.4%, which is below the market average for Cash ISAs and sits 1.85% behind the category leader at 5.25%, so I would not call this a standout rate. It does at least edge ahead of August 2026 CPI inflation of 3.1% by 0.30%, meaning your money is just about holding its real value. The account accepts transfers in and opens with as little as £1, which suits savers who want flexibility, but if the rate is your priority, Octopus Money's Cash ISA at 3.44% is worth a look.

Compare Cash ISAs

2 alternatives to Harpenden Building Society's Online ISA

Same type of account, closest on rate.

Common questions about the Online ISA

D

DepositScout Alerts

Example alert

Easy Access rate just dropped

A top provider just cut their rate. Here's what you need to know about the latest market shift.

Example Easy Access Saver Rate Down
4.20% AER
4.75%
View Best Rates
Live Market Tracking

Be the first to know when this Harpenden Building Society rate drops.

Join 1,000+ savers using DepositScout who get instant email alerts when top UK savings rates change. Never miss out on a better deal again.

Takes 30 seconds · No spam · Unsubscribe any time