When the NS&I dropped the Premium Bonds prize fund rate from 4.15% to 3.8% on 1 May 2026, the response across UK personal finance forums was predictable: a wave of "moving my £40k to Chase 5% easy access" posts. What almost nobody clicked on was the obscure sub-page where NS&I quietly relaunched the index-linked savings certificate for new money — closed to new investors since 2011, reopened on 15 April 2026 with a five-year fixed term at RPI plus 0.5%.
If RPI averages 3.9% across the next five years — which is roughly where every major UK forecaster is sitting in May 2026 — the certificate returns about 4.4% tax-free. Outside an ISA, for a higher-rate taxpayer, that is the equivalent of a 7.3% gross return on a fixed-rate bond. There is no product on the UK market that matches it, and the £15,000-per-year subscription cap has not been raised in fifteen years — meaning a couple can shelter £30,000 a year, £150,000 over five years between two ISA allowances and the certificate cap.
Why the certificate is the better hedge than a fixed-rate ISA right now
The case is straightforward. A five-year fixed-rate cash ISA in May 2026 pays around 4.45% — fine if you believe inflation will average 3% or less. If RPI comes in higher (and the Bank of England's own May Monetary Report puts the upper band at 4.7% on services inflation), the ISA loses real purchasing power while the certificate matches it pound-for-pound.
The catch — and there are two
First, you cannot withdraw the money during the term without losing the index-linking. Treat it as a five-year commitment.
Second, the certificate is non-transferable on death except to a spouse — if you die mid-term, your estate inherits the cash value, not the bond, which interrupts the tax-free compounding. For older savers with IHT planning concerns, this is a serious disadvantage versus a SIPP or a Premium Bond holding (which can be retained by the executors until probate).
Green Savings Bond 4th issue — the boring sibling
NS&I also relaunched the Green Savings Bond on 1 May 2026 with a 3-year fixed rate of 4.05%, tax-free for ISA investors only (if held outside an ISA it counts toward the £1,000 personal savings allowance). For a basic-rate taxpayer with savings spilling outside an ISA, this is now the best non-index-linked NS&I product on offer — and uniquely, it carries the full 100% Treasury guarantee, not just the £85,000 FSCS limit.
What to actually do this week
Higher-rate taxpayer with £15,000 of "spare cash" sitting in a low-paying easy-access account: subscribe to the index-linked certificate before the year-end allowance window. Basic-rate taxpayer with similar cash and a longer horizon: the Green Savings Bond at 4.05% beats almost every named-brand savings bond at the same term. Either way, the NS&I app finally added a working transfer-in flow in March 2026, so the whole subscription takes under ten minutes.