Cash ISA

Harpenden Building Society 90 Days' Notice ISA Review

A top-paying notice cash ISA from Harpenden Building Society, with a £1,000 minimum deposit. None of the other 20 notice cash ISAs we track pays more.

Variable rate

4.04%AER

Rate checked Oct 2026Got this account? Leave a review

Protection

FSCS£120,000

Min balance

£1,000

Max balance

£250,000

Access

90 Days

Interest paid

Annually

Transfers in

Accepted

How It Stacks Up

Ranks 1st of 21

Notice cash ISAs we track

Top rate
This account 4.04%
UK CPI (Aug 2026)
3.10%
Pays 0.94% more
Average notice cash ISA
3.17%
Pays 0.87% more
Best notice cash ISA
4.04%
About the same

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

Compare cash ISAs

A Good Fit For

  • Pro: New and existing savers

Worth Weighing Up

  • Con: The rate is variable, so it can go down
  • Con: You need at least £1,000 to open it

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Estimated returns with Harpenden Building Society's Cash ISA

What you could earn with Harpenden Building Society's 90 Days' Notice ISA.

Estimated interest

£1,000 saved

£40.40

At 4.04% AER

£5,000 saved

£202

At 4.04% AER

£10,000 saved

£404

At 4.04% AER

£250,000 saved

£10,100

At 4.04% 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 90 Days' Notice ISA

Jan WatermannCo-Founder, DepositScout

Harpenden Building Society's 90 Days' Notice ISA pays 4.04%, which sits 1.21% below the Cash ISA market leader at 5.25%, and the position data confirms it is below the market average, so I would not choose it on rate alone. That said, 4.04% does beat August 2026 CPI of 3.1% by 0.94%, so your money keeps real value. The account accepts transfers in and needs at least £1,000 to open. The genuine catch is the 90-day notice period, which rules it out if you might need quick access.

Compare Cash ISAs

Common questions about the 90 Days' Notice ISA

D

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