Premium Bonds vs Savings Accounts UK: The 4.35% Prize Rate Rewrites the Breakeven

The prize fund rate is the total value of prizes paid out as a share of all eligible Bonds in a year. NS&I states the odds plainly: 21,000 to 1 for every £1 Bond, every month, variable. That is better than the 23,000 to 1 of the April draw, but it is still a lottery ticket, not a savings rate.

September's draw shows what the average hides. NS&I paid £497,086,175 across 6,529,868 prizes. Two people won £1 million. Ninety-five won £100,000.

Now look at the bottom of the distribution: 6,446,807 of the 6,529,868 prizes — 98.7% — were worth £100 or less. The two £1 million jackpots that make 4.35% mathematically true are two tickets out of 6.5 million.

The honest way to think about Premium Bonds is the median, not the mean. A holder with £1,000 might win nothing for months. A holder with the full £50,000 can expect the mean to assert itself over time, but the distribution stays right-skewed — a handful of big wins, millions of £25s.

The other side of the comparison has repriced since April. MoneySavingExpert's best-buy tables, updated 16 September, show:

• Easy access: Spring and Cahoot both pay 5% — but only on the first £3,000 to £5,000. Chase pays 4.5% on up to £3 million.
• One-year fix: Investec pays 5%; NS&I pays 4.82%.
• Five-year fix: West Brom Building Society pays 5.2%.
• Cash ISA: Tembo pays 4.62% easy access, within the £20,000 allowance.

The 5% easy-access headline is real but capped. Above £5,000 you are looking at roughly 4.5% for instant access. That distinction matters when you run the breakeven below.

NS&I's own variable accounts are no longer the benchmark either. Direct Saver now pays 3.75% and Direct ISA pays 3.80% — both below Premium Bonds' 4.35% and below the best open-market accounts. Bank deposits are protected by the FSCS up to £120,000 per person per banking group; Premium Bonds are backed by HM Treasury with no upper limit. See our FSCS guide for the detail.

On £10,000, the pre-tax numbers look like this:

A 4.5% easy-access account pays £450. A 5% one-year fix pays £500. Premium Bonds' 4.35% expected return is £435 — and "expected" is the mean, not a promise. For a basic-rate taxpayer with £10,000, the savings account wins outright: £500 of interest sits inside the £1,000 Personal Savings Allowance, so none of it is taxed.

The comparison changes with balance. At the full £50,000 Premium Bonds holding, the expected return is £2,175. A 4.5% easy-access account pays £2,250 gross, and a 5% fix pays £2,500 gross. Before tax the accounts still win. After tax, the picture flips for anyone paying more than the basic rate — which is the next section.

Premium Bond prizes are free of Income Tax and Capital Gains Tax, at every tax band, no matter how large. Savings interest is income, and the Personal Savings Allowance only shields £1,000 for basic-rate taxpayers, £500 for higher-rate and nothing for additional-rate.

Take £50,000, the maximum Premium Bonds holding. A 4.5% easy-access account earns £2,250. After the allowance, a basic-rate payer keeps £2,000, a higher-rate payer £1,550 and an additional-rate payer £1,237.50. Premium Bonds' expected £2,175 beats all three — by £175, £625 and £937.50.

Even a 5% one-year fix, which pays £2,500 gross, nets only £2,200 after tax for a basic-rate payer, £1,700 for higher-rate and £1,375 for additional-rate. The fix edges Premium Bonds by £25 for basic-rate savers, then loses by £475 and £800 further up the bands.

One caveat matters more than any chart: the first £20,000 belongs in a Cash ISA, not Premium Bonds. A 4.62% cash ISA pays £924 on £20,000 with zero tax and no lottery. Premium Bonds are what you do with the cash above the ISA line.

Premium Bonds win when you are a higher or additional-rate taxpayer holding cash above the ISA allowance and the Personal Savings Allowance. That is the only group for whom the after-tax maths clearly favours the draw. The Treasury backing — unlimited, versus the £120,000 FSCS cap — adds a second reason if you are holding more than £120,000 in one banking group.

Savings accounts win when you are a basic-rate taxpayer, or when you need a known number in 12 months. A 5% fix pays a guaranteed £500 on £10,000 with none of the variance. Premium Bonds cannot give you that.

For most people the answer is a combination, not a contest. Fill the ISA, keep your emergency fund in instant access, and only then weigh Premium Bonds against a taxable account. For a worked example of the £20,000 decision, see Premium Bonds vs Cash ISA: the maths on £20,000.

Neither product is immune from August's inflation. CPI rose to 3.1% in August, up from 2.9%, driven by a 23% rise in motor fuel prices. The Bank of England base rate has sat at 3.75% since December, and the Monetary Policy Committee decides tomorrow.

A 4.35% Premium Bonds expected return minus 3.1% inflation leaves 1.25% of real purchasing power — before you account for the fact that you will not actually receive the average. A 4.5% easy-access account leaves 1.4% real, gross of tax. After tax at the additional rate, that 4.5% becomes 2.475%, which loses to inflation outright.

That is the sharper point. Cash now treads water against 3.1% CPI, and for additional-rate taxpayers it sinks. Premium Bonds do not fix inflation — nothing tax-free at 4.35% does — but their tax exemption is worth more when every basis point counts. For more on how the rate cycle feeds savings, see the savings hub.