Ranked by rate alone. No paid placements: who pays us has no say in the order.
Read from each bank's own website, 3 November 2026. Accounts open to new customers.
18 months fixed cash ISAs
Tax-free, fixed for about 18 months. Early access usually costs some interest.
15 accounts, highest AER first
18 months fixed cash ISAs, ranked by AER, highest first. Top 5 shown
Rank#
Account
AER
Min to open
1
Aldermore 15 Month Fixed Rate Cash ISAFixed for 15 months · from £1,000Beats inflationAged 18+, UK resident and only UK tax residentDetails for Aldermore 15 Month Fixed Rate Cash ISA
Access
No withdrawals until the term ends.
Conditions
Aged 18+, UK resident and only UK tax resident. Not available to US Persons or in trust.
Interest paid
Once a year
Manage by
Online
FSCS licence
Aldermore Bank PLC
Deposit-taker
Aldermore, a trading name of Aldermore Bank PLC
Incorporated in
United Kingdom
Regulated
Yes, by the Prudential Regulation Authority and Financial Conduct Authority (FRN 204503)
Protection and disputes
Financial Services Compensation Scheme and Financial Ombudsman Service
Capital
Paid-up capital and reserves of £1,370m at 30 June 2024 (latest published accounts).
Withdrawals before the term ends are subject to 90 days' loss of interest.
Maximum
£500,000
Conditions
Interest annually at the AER shown, or monthly at a lower rate. Apply online or by post. Minimum £500 read on the 1 Year Fixed Cash ISA page; assumed the same for this term.
Interest paid
Once a year
Manage by
Online, Post
FSCS licence
Paragon Bank PLC
Deposit-taker
Paragon Bank, a trading name of Paragon Bank PLC
Incorporated in
United Kingdom
Regulated
Yes, by the Prudential Regulation Authority and Financial Conduct Authority (FRN 604551)
Protection and disputes
Financial Services Compensation Scheme and Financial Ombudsman Service
Capital
Paid-up capital and reserves of £1,046m at 30 September 2025 (latest published accounts).
Highest AER first, then the lower minimum deposit. Ranking rules version 1.2.0. AER shows what you'd earn in a year including any bonus. Rates can change at any time: check with the bank before you apply. Lifetime ISA rates are the provider's interest only; the government's 25% bonus is not in the AER. Lifetime ISAs, Junior ISAs and children's accounts are ranked only against their own kind, and Premium Bonds, which pay prizes rather than interest, are never ranked: see NS&I and Premium Bonds. NS&I accounts are backed by HM Treasury, not the FSCS. We list accounts held directly with the bank, not savings sold through apps and platforms such as Revolut, Trading 212 or Raisin. "Beats inflation" means the AER, and the rate after any bonus, is above CPI inflation of 3.5% (September 2026, ONS), before tax. How we rank, what we don't list and how we're paid.
