Premium Bonds or a Cash ISA -- which is better for my savings?

Full answer

Premium Bonds and Cash ISAs are both extremely popular, low-risk, tax-free UK savings options, but they work in fundamentally different ways, making the "better" choice highly dependent on your personal circumstances and risk appetite. **How Premium Bonds work** Each £1 Premium Bond you hold (minimum purchase £25, maximum holding £50,000 per person) is entered into a monthly prize draw, with tax-free prizes ranging from £25 up to two £1 million jackpots each month. NS&I publishes an "annual prize fund rate" which represents the average return across all bondholders if the odds played out perfectly, but this is NOT a guaranteed interest rate -- some bondholders in any given year will win nothing at all, while a lucky few win substantially more than the average rate would suggest, and NS&I is 100% government-backed, so your capital itself is completely safe. **How a Cash ISA works** A Cash ISA pays a known, guaranteed interest rate (fixed or variable depending on the specific account) on your full balance, entirely free of tax, up to the £20,000 total ISA allowance across ISA types each tax year. Unlike Premium Bonds, every saver with the same balance and rate earns the same guaranteed return -- there's no lottery element, but also no chance of an outsized win. **Tax treatment -- both are tax-free, but differently relevant** Premium Bond prizes are always entirely tax-free for everyone, regardless of your other income or existing Personal Savings Allowance usage. Cash ISA interest is also always tax-free -- but crucially, ordinary (non-ISA) savings accounts ALSO offer a Personal Savings Allowance (up to £1,000 tax-free interest for basic-rate taxpayers, £500 for higher-rate, £0 for additional-rate), meaning many basic-rate taxpayers with modest savings might not actually save any extra tax by choosing a Cash ISA over a competitive ordinary savings account -- Premium Bonds' tax-free status therefore matters most to additional-rate taxpayers or those with larger savings balances who would otherwise exceed their Personal Savings Allowance. **Expected returns comparison** Over the long run and across a large pool of Premium Bond holders, the AVERAGE return should track the published prize fund rate, but for smaller individual holdings the actual outcome is highly variable and often below average, since a small proportion of bonds win the large prizes that pull the average up -- if you hold, say, £1,000-£5,000 in Premium Bonds, don't be surprised if your actual annual "return" (measured by prizes won) is noticeably below the headline rate, or even zero in some years, due to the random nature of the draw. **Which suits which saver** Cash ISAs suit savers who want certainty and predictable growth, particularly for money earmarked for a specific near-term goal. Premium Bonds suit savers who enjoy the excitement of the prize draw, want completely guaranteed capital security with tax-free upside potential, or have already used their full ISA allowance elsewhere and want another tax-free option for additional savings. **Practical tip** Many savers use both -- filling their Cash ISA allowance for guaranteed tax-free growth on their core emergency fund, while holding additional savings in Premium Bonds for the tax-free prize potential once their ISA allowance is used up, or simply for the enjoyment factor of the monthly draw.

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