What interest rate does the TSB 18 Month Fixed Rate Cash ISA pay?

The TSB 18 Month Fixed Rate Cash ISA pays 4.60% AER fixed.

How much interest could I earn?

Saving £10,000 for 18 months would earn about £698 at 4.60% AER. This assumes the rate stays the same and interest stays in the account.

How much can I pay in?

You can deposit at least £1 and up to £1,000,000.

When is interest paid?

You can choose to have interest paid monthly or at the end of the term.

Who can open this account?

New and existing TSB customers can open it. You can open it online or in branch.

Is my money protected?

Yes. Eligible deposits are protected by the Financial Services Compensation Scheme (FSCS) up to £120,000 per person, per banking licence.

Can I transfer an existing ISA in?

Yes, transfers in from other ISAs are accepted.

How does it compare with other 18-month cash ISAs?

At 4.60% AER it ranks 1st of 4 18-month cash ISAs we track. The best pays 4.60% and the average is 4.30%.

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Cash ISA

TSB 18 Month Fixed Rate Cash ISA Review

Q: Can I withdraw my money?

Access: No withdrawals without a penalty.

A top-paying 18-month cash ISA from TSB. None of the other 3 18-month cash ISAs we track pays more.

Rate checked Oct 2026Got this account? Leave a review

Fixed rate · 18 months

4.60%AER

Rate checked Oct 2026Got this account? Leave a review

Protection

FSCS£120,000

Min balance

£1

Max balance

£1,000,000

Access

No withdrawals without a penalty

Interest paid

Monthly/On maturity

Transfers in

Accepted

How It Stacks Up

Ranks 1st of 4

18-month cash ISAs we track

Top rate

This account 4.60%

UK CPI (Aug 2026): 3.10%; Pays 1.50% more
Average 18-month cash ISA: 4.30%; Pays 0.30% more
Best 18-month cash ISA: 4.60%; About the same

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

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A Good Fit For

Pro: New and existing savers
Pro: Savers who want a monthly income

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Estimated returns with TSB's Cash ISA

What you could earn with TSB's 18 Month Fixed Rate Cash ISA.

Estimated interest

£1,000 saved

£69.79

At 4.6% AER

£5,000 saved

£349

At 4.6% AER

£10,000 saved

£698

At 4.6% AER

£1,000,000 saved

£69,788

At 4.6% AER

Estimated over the 18-month term, 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 TSB 18 Month Fixed Rate Cash ISA

Jonny PeaseCo-Founder, DepositScout

TSB's 18 Month Fixed Rate Cash ISA pays 4.60%, which sits near the market average for cash ISAs and is 0.52% behind the category leader at 5.12%, so it is not a standout rate. That said, 4.60% does beat August 2026 CPI of 3.1% by 1.50%, meaning your money grows in real terms. The account accepts transfers in and is open to existing customers, but the real catch is the early access penalty of 135 days' interest on any amount withdrawn, so it suits savers who are confident they can lock money away for the full 18 months.

Compare Cash ISAs