Premium Bonds Pay Tax-Free Outside Your £20,000 ISA Allowance — A 4.51% Cash ISA Stops Working the Day You Save Above £20,000

The 2026/27 ISA allowance is £20,000, unchanged since 2017. For a saver with £15,000 of cash, the conversation begins and ends at the cash ISA — they should use it, fill it, and stop reading. For the saver with £40,000, £60,000, or £100,000 in cash savings, the cash ISA can absorb £20,000 a year and no more. The remaining capital has to live somewhere.

The options for that excess capital are limited. A non-ISA easy-access savings account at 4.51% is the headline alternative. But interest above the Personal Savings Allowance is taxable: £1,000 free for basic-rate taxpayers, £500 free for higher-rate, £0 free for additional-rate. A higher-rate saver with £30,000 in a 4.51% non-ISA account earns £1,353, of which £853 is taxable at 40% — £341 of tax owed.

Premium Bonds skip that entirely. Every prize is tax-free. It does not count against the PSA. It does not appear on Self Assessment. For the higher-rate saver with capital above the ISA allowance, the comparison is not 4.51% vs 3.30% — it is 4.51% minus 40% tax (effective 2.71% on the portion above PSA) versus 3.30% tax-free. Premium Bonds win that comparison.

The Financial Services Compensation Scheme protects £120,000 of cash deposits per authorised banking licence (raised from £85,000 in December 2025). For most savers that is more than enough. For the saver holding £200,000 in cash — sale proceeds, inheritance, end-of-life simplification — the FSCS cap forces the awkward shuffle of accounts across multiple banking licences.

NS&I is different. It is backed 100% by HM Treasury — every penny, no cap. Premium Bonds (capped at £50,000 per holder), Direct Saver (capped at £2 million), Direct ISA (capped at £20,000 per tax year). NS&I's own marketing line is direct: "Most banks only guarantee your savings up to £120,000. We're the only provider that secures 100% of your savings above this amount."

For the saver above the FSCS cap, that matters. The 1.21-percentage-point rate gap on £50,000 of Premium Bonds is £605 a year. The peace of mind of 100% government backing on £50,000 of capital is worth real money to a buyer who has actually thought about counterparty risk. The 2008 crisis, the 2023 mini-banking-crisis in the US, and the regular small-bank failures in the UK are not theoretical events.

This matters for a specific buyer: the saver above £120,000 in cash, who values predictability and government backing more than the small rate uplift of an extra cash ISA at a regional building society.

Premium Bonds are one of only two NS&I products that pay returns entirely outside the ISA wrapper while remaining tax-free. The other is the tax-free Savings Certificate family, which has been closed to new investments for years.

For the saver who has already maxed the £20,000 ISA allowance on a stocks & shares ISA — which is what the long-term saver should do, given the historical real return of equities versus cash — Premium Bonds are the cleanest tax-free home for the cash component of their portfolio. Every pound there is sheltered from income tax on interest, sheltered from capital gains tax on prizes, and not counted against PSA.

The order of operations for a saver with £40,000 of capital, looking at what to hold in cash:

1. Decide how much should be in cash at all. A long-term saver should weight toward equities; the cash component is for emergencies and short-term goals.
2. Use the £20,000 ISA allowance. Most savers do best putting this in stocks & shares — see our argument in £20,000 in a 4.51% Cash ISA Becomes £31,048 in a Decade — The Same Money in Global Equities Becomes £47,347. The cash component goes outside the ISA wrapper.
3. Hold cash where the after-tax return is highest. Below the PSA, that's any easy-access account at 4.51%. Above the PSA — and for higher-rate taxpayers, that is most cash savers — Premium Bonds become competitive because the prizes are tax-free.
4. For the saver who specifically wants a cash ISA, NS&I's Direct ISA at 3.50% is government-backed but rate-uncompetitive — the building societies pay more. The cash ISA is best done at the highest-paying provider, with a separate Premium Bonds holding for above-allowance cash.

Two £1 million prizes are paid out every month. The total prize fund pays out roughly 5.7 million prizes per draw against ~109 billion eligible bonds. The headline odds are long but well-defined.

A £50,000 holder — the maximum permitted — has 50,000 entries per draw, 600,000 entries a year. The probability of any prize in a year is essentially 100% — the binomial concentrates around 26 expected prizes annually. The probability of an unusually good year (45+ prizes) is around 5%. The probability of winning the £1m in any given year is roughly 1 in 91,000.

For most savers, that lottery component is a curiosity, not a reason to buy. For one specific buyer it is a real feature: someone with £50,000+ in cash above their ISA allowance, who is happy with the expected 3.30% tax-free, and who values the small but real chance of a tax-free £1m far more than the 1.21-percentage-point rate gap costs them.

The rational case is not "buy Premium Bonds because you might win £1m". It is "buy Premium Bonds because the expected tax-free return is competitive with after-tax non-ISA savings for higher-rate taxpayers, and the £1m draw is a free option on top". That option has positive expected value over a long enough horizon — it is not negative-expectation gambling like the National Lottery.

Premium Bonds belong in a portfolio in three specific situations:

The above-allowance saver. Anyone with more than £20,000 in cash needs somewhere for the excess. Above the £500-£1,000 PSA, Premium Bonds are tax-competitive with non-ISA savings for higher-rate taxpayers and offer NS&I's 100% government backing.

The above-FSCS saver. Anyone with more than £120,000 in cash at a single banking licence runs counterparty risk. NS&I's no-cap government backing matters at this level. Premium Bonds absorb up to £50,000 of that excess.

The unable-to-resist-the-£1m saver. Some savers will hold Premium Bonds for the lottery component regardless of the math. For them, the right answer is to cap the holding at the level where the expected return matches the alternative — usually around £20,000-£30,000 — and treat the rest as a known cost for a very small lottery exposure. Better than buying lottery tickets.

For the /savings/ saver below £20,000 in total cash, the cash ISA at 4.51% is the right answer. Use the /tools/cash-isa-comparison tool to find the best provider. For everyone above that bar, Premium Bonds belong in the mix — not as a substitute for the cash ISA, but as its complement above the £20,000 wrapper limit.

A serious saver with £50,000 in cash should hold roughly:

• £20,000 in the highest-paying cash ISA they can find (4.51% easy-access from a competitive building society)
• £20,000-£30,000 in Premium Bonds, particularly if higher-rate taxpayer
• The remainder in a non-ISA easy-access account up to the PSA limit

This portfolio uses every tax shelter available, holds capital in the right wrappers, and gives the saver a meaningful stake in the £1m draw at zero cost above the alternative. The cash ISA evangelists who insist Premium Bonds are always wrong are arguing against a strawman — Premium Bonds are not competing with the cash ISA at the £20,000 level. They are competing with non-ISA savings at the £20,000+ level, and at that level, for the right tax bracket, they win.

For the same-day case against Premium Bonds — that the median small holder wins nothing while the cash ISA pays £902 a year, every year — see Premium Bonds Pay 3.30% to the Lucky and £0 to the Median Holder. For more on building the cash component of a serious portfolio, see Cash or Investments? The 2026/27 Decision Framework Every Saver Needs and the /savings/ hub.

This article is for informational purposes only and does not constitute financial advice. Rates, tax rules, and FSCS limits change — verify current Premium Bonds prize fund rates with NS&I, current cash ISA rates with the providers directly, and your tax situation with HMRC or a qualified adviser. You should seek independent financial advice before making any investment decisions. The expected return on Premium Bonds is variable; actual returns depend on the prize draw and may be substantially below the headline 3.30% rate, particularly for smaller holdings.