Premium Bonds: Expected Returns vs Guaranteed Interest

Premium Bonds are advertised with a headline figure called the prize fund rate. It looks like a savings rate and is naturally read as one. It is not. It is the annual rate applied to the total value of all eligible Bonds to size the monthly prize pot — a pooling figure, not a payment to any individual.

This guide sets out the comparison that matters when weighing Premium Bonds against an account paying guaranteed interest: what the prize fund rate does and does not tell you, why the typical holder receives less than it, and when the tax-free treatment of prizes changes the arithmetic. It does not recommend a course of action or a provider.

The Premium Bonds prize fund rate is 3.80%, applying from the July 2026 draw, with odds of 22,000 to 1 for each eligible £1 Bond in each monthly draw. Both are variable — the rate was 3.30% with odds of 23,000 to 1 from the April 2026 draw. Always check NS&I's current published figures rather than a remembered number.

A guaranteed savings rate is a promise: deposit a sum, hold it, receive that return. The prize fund rate merely describes how a pot is sized and then distributed at random. Because a small number of very large prizes — including two £1 million jackpots each month — pull the average upwards, the typical holder receives less than 3.80%, and a holder with a modest balance may receive nothing across a full year. No return is guaranteed over any period.

NS&I takes the total value of all eligible Bonds across every holder in the country and applies the prize fund rate to that total to determine the size of the monthly prize fund. That fund is split into individual prizes ranging from £25 up to £1 million, and those prizes are allocated at random by ERNIE, the draw's random number generator.

The rate is therefore accurate at the level of the whole scheme. Add up every prize paid over a year, divide by the total value of all eligible Bonds, and you arrive at approximately the prize fund rate. What it cannot tell you is how that money is distributed between the millions of people holding Bonds — and the distribution is extremely uneven.

This is the opposite of how a conventional interest rate behaves. With an interest-bearing account, the advertised AER is both the scheme average and the individual outcome, because everyone receives the same rate on their balance. With Premium Bonds those are different things, and only the first is published.

The prize fund rate is a mean — a total divided by a headcount. The figure that describes a typical experience is the median: the outcome of the holder sitting exactly in the middle, with half doing better and half doing worse.

When a distribution contains rare very large values, the mean sits above the median. Two £1 million jackpots each month, plus a tier of six- and five-figure prizes, absorb a meaningful share of the fund and hand it to a handful of people. Everyone else divides a remainder dominated by £25 prizes. The jackpots drag the mean up; they do not move the median. NS&I does not publish a median return.

The size of the gap depends almost entirely on how many Bonds you hold, since each £1 Bond is one independent entry. The table below is derived from the published odds of 22,000 to 1 per Bond per draw, treating draws as independent. It shows expected prize counts, not amounts.

Two things follow. For a holder with £1,000, the most likely annual outcome is nothing at all — making the median return for that group zero, against a headline of 3.80%. And even at the £50,000 maximum, where prizes arrive reliably, the arithmetic does not automatically reach the headline: roughly 27 prizes a year at the smallest £25 denomination comes to about £680, or 1.4% on £50,000. Reaching 3.80% requires catching prizes above the bottom tier. Some holders do; the median holder captures part of that gap, not all of it.

The honest comparison is not "3.80% versus the savings rate on offer". It is between a certain outcome and a probability distribution. A guaranteed rate delivers a known figure. Premium Bonds deliver a range whose lower end is £0 and whose upper end is £1 million, with the overwhelming weight of probability sitting at the bottom. Two savers with identical balances and holding periods can end the year with entirely different outcomes.

There is also no compounding unless you create it. Interest in a savings account is credited to the balance and earns further interest, which is why AER exceeds the gross rate on accounts paying more often than annually. Premium Bond prizes compound only if you elect to reinvest them into new Bonds, and only up to the £50,000 ceiling.

Set against that, the capital position is unusually strong. NS&I is backed by HM Treasury, so the money itself is secure with no upper limit — a broader protection than the FSCS deposit limit applying across banks and building societies. Premium Bonds are excluded from the FSCS because the Treasury guarantee sits behind them instead. What is guaranteed is the return of your capital, not a return on it.

All Premium Bond prizes are free of UK Income Tax and Capital Gains Tax, and they do not count towards the Personal Savings Allowance. This is a real advantage, but it only alters the comparison for people who would otherwise be paying tax on their savings interest.

The Personal Savings Allowance gives basic rate taxpayers £1,000 of tax-free savings interest a year, higher rate taxpayers £500, and additional rate taxpayers nothing. Below those thresholds, and inside an ISA, interest is already tax-free — so the tax-free status of prizes adds nothing you did not already have.

The picture changes for someone who has used their full £20,000 ISA allowance, exhausted their Personal Savings Allowance, and is taxed at the margin on every further pound of interest. For a higher rate taxpayer, a taxable 4.00% account nets 2.40%; for an additional rate taxpayer with no allowance, 2.20%. Against those net figures a tax-free 3.80% average looks more competitive — though it remains an average, not a promise, and the median outcome still applies.

So the questions must be answered in order. Would you be taxed on the interest at all? If not, the headline advantage largely disappears. If so, run the comparison against the after-tax rate rather than the advertised one — the same discipline that applies when weighing a Cash ISA against a taxable account, or when savings interest has pushed income into a higher band.

The minimum holding is £25 and the maximum is £50,000 per person, with Bonds bought in whole pounds. Newly purchased Bonds must be held for one full calendar month before entering a draw, so money parked briefly earns nothing at all. Anything above £50,000 remains capital-secure but is not entered into the draw, so excess balances earn a guaranteed zero.

Because both the odds and the prize fund rate are variable, a comparison made today can be overturned by an NS&I announcement — as the moves from 3.60% to 3.30% and then to 3.80% across 2026 demonstrate. If you are already holding and simply not winning, what to do about a long run without prizes is a separate question worth reading alongside this.

Looking for more on this topic? Browse all our savings guides.

This guide is based on NS&I's published product terms and UK tax legislation. The following sources cover the rules described above:

• NS&I — Premium Bonds
• NS&I Corporate — prize fund rate and odds announcements
• HM Revenue & Customs
• Income Tax (Trading and Other Income) Act 2005
• Financial Services Compensation Scheme

Free, impartial money guidance is available from MoneyHelper, the government-backed service run by the Money and Pensions Service.

Related: Premium Bonds Not Winning? | Personal Savings Allowance Explained | AER vs Gross Rate | All savings guides.