Cash ISA rates have reached a notable 5% milestone, marking the first time in over 15 months that tax-free savings accounts have offered such returns. Plum and Trading 212 have both announced updated interest rates for their flexible cash ISAs, with Plum offering 5% and Trading 212 offering 5.01%. This increase comes as inflation is expected to rise further, providing a significant boost for savers looking to maximize their returns on tax-free savings. According to Moneyfacts data, the last time variable rate Cash ISAs were paying 5% or more was June 2025. Plum's 5% offer is available for only five days, ending on 30 September 2026, while Trading 212's rate offering has no set end date. Both accounts are variable rates, which could change if the Bank of England base rate is altered. They also include bonuses that last for one year, after which the underlying rates are 2.54% with Plum and 3.6% with Trading 212. It's important to note that the 5% rates are only applicable to new money, meaning cash sent into a new Cash ISA for this tax year. Transfers to these accounts will receive different rates, with Plum offering 3.75% on transferred funds. To achieve the Plum bonus, customers need to keep the account for 12 months and meet other conditions. Adam French, head of consumer finance at Moneyfactscompare.co.uk, advised savers to act quickly, as the 5% return is only available to new customers who open a Cash ISA with Plum via its mobile app between 25 and 30 September 2026. This limited-time offer highlights the current competitive landscape in the savings market, where high returns are becoming more accessible for those looking to take advantage of the temporary rates.