Educational use only. Not financial, investment, tax or legal advice.

3 August 2026 Syd Lawrence 5 min read

The PSA Trap: When Your Savings Interest Becomes Taxable

Higher-rate taxpayers get a £500 Personal Savings Allowance. Additional-rate taxpayers get £0. Here is what that costs in real pounds, and the ISA fix that removes the question.

Syd Lawrence

CEO & Co-founder at Delphina

Syd got fed up with being kept confused by the UK personal finance industry. So he built the tool he wished existed. Qualified to provide financial advice, prefers to provide financial clarity. No agenda. Just someone who finally got clear and wanted everyone else to be able to too.

You are a higher-rate taxpayer with £50,000 in savings earning 4.5%. The same pot pays you £1,012 less a year than it pays a basic-rate taxpayer.

The Personal Savings Allowance is the chunk of interest the government lets you earn before tax kicks in. £1,000 for basic-rate, £500 for higher-rate, £0 for additional-rate. At today's rates, those thresholds are easy to cross. The trap is that your bank does not warn you. HMRC does, in a brown envelope, around ten months later.

You opened the savings account because the rate was competitive. You have been putting £500 a month in for the last three years. The balance is up. The statement looks healthy. You have not done the maths on what the tax bill looks like.

Most people in this position have no idea the trap exists until HMRC sends a tax code adjustment or a Self Assessment demand. The bank does not withhold tax on savings interest. The liability is yours.

Here is what the trap costs, who it catches, and the single action that removes it.

What the Personal Savings Allowance actually is

The PSA is the amount of savings interest you can earn in a tax year before paying income tax on it. The amount depends on your highest rate of income tax.

Tax band	Income tax rate	PSA
Basic-rate	20%	£1,000
Higher-rate	40%	£500
Additional-rate	45%	£0

Most basic-rate taxpayers with a savings pot under £22,000 at 4.5% never breach the PSA. The trap closes around higher-rate and additional-rate taxpayers with pots the banks have paid them to build.

The numbers, by tax band, on a £50,000 pot at 4.5%

Annual interest: £2,250. The same pot, the same rate, three different outcomes depending on your tax band.

Tax band	PSA	Taxable interest	Tax owed	Net interest
Basic-rate	£1,000	£1,250	£250	£2,000
Higher-rate	£500	£1,750	£700	£1,550
Additional-rate	£0	£2,250	£1,012.50	£1,237.50

The additional-rate taxpayer earns £762.50 less than the basic-rate taxpayer on the same money, in the same year, from the same bank. The tax bands are doing that. Not the bank. Not the rate.

Who the trap catches

The PSA trap does not catch everyone. It catches people with the right combination of tax band and savings pot. The four most common groups:

Higher-rate earners with £15,000+ in non-ISA savings
Retirees who have drawn a tax-free pension lump sum and parked it in a savings account
People who received an inheritance and have not yet decided where the money belongs
Anyone with a savings pot that has quietly crossed the PSA threshold because rates rose while the pot stayed put

If you have had a life event in the last three years (retirement, inheritance, redundancy, a bonus that pushed you into a higher band) your tax position may have changed. The PSA follows your income tax band, not your savings history.

How the tax is actually collected

Banks do not withhold tax on savings interest. You receive the gross interest, and if you owe tax, you tell HMRC through your Self Assessment tax return. In practice:

Your bank pays you the full gross interest
You register for Self Assessment if you are not already in it, or include the interest on your existing return
HMRC calculates the tax due and sends a bill
You pay by 31 January the following year

Some banks will issue a tax code adjustment instead, which collects the tax through your salary. Either way, the liability is yours. The bank's job is to pay you interest and report the gross amount to HMRC. The tax calculation is not theirs.

The fix: move the pot into a cash ISA

A cash ISA pays interest that is automatically tax-free. No PSA calculation. No Self Assessment adjustment. No brown envelope.

The trade-off: ISA rates are usually slightly lower than the equivalent non-ISA rate. The gap is smaller than most people expect in 2026.

Account type	Top non-ISA	Top cash ISA	Gap
One-year fixed	4.9%	4.6%	0.3%
Easy access	4.5%	4.1%	0.4%
Two-year fixed	4.7%	4.4%	0.3%

On a £50,000 pot, the 0.3 percentage point gap on a one-year fix costs £150 a year in foregone interest. The tax bill you avoid is £700. The cash ISA wins by £550 a year on this pot. The maths is not subtle.

The decision framework, by tax band

Basic-rate taxpayer

The £1,000 PSA covers most pots under £22,000 at 4.5%. Non-ISA is fine for these. Once the pot crosses £22,000 the ISA conversation becomes worth having. Most basic-rate savers never cross it.

Higher-rate taxpayer

The £500 PSA only covers roughly £11,000 at 4.5%. Above that, the ISA wins on a 20 percentage point tax differential. The general rule: ISA anything over £15,000 in non-ISA savings.

Additional-rate taxpayer

The PSA is £0. All non-ISA interest is taxable at 45%. ISA only, for any meaningful pot. There is no scenario where a non-ISA savings account makes sense for an additional-rate taxpayer with substantial savings.

What to do this week

Four actions. The first is the one that moves the dial.

One action this week

Add up every non-ISA savings account you hold. Current account savings pots, fixed-rate bonds, NS&I accounts, easy-access accounts. Get the total.
Multiply the total by your current rate. That is your gross annual interest. Compare it to your PSA (£1,000, £500 or £0).
If the gross interest exceeds your PSA, open a cash ISA and move enough to keep your non-ISA interest below the threshold. Most providers allow partial transfers, so you do not have to move the whole pot.
If your tax band has changed in the last three years (promotion, bonus, redundancy, retirement), check your current tax code with HMRC. A stale tax code is how most people land in the trap without realising.

For the wider picture on ISA timing, the best ISA strategy for 2026/27 walks through the £20,000 allowance and what to prioritise before 5 April 2027. For the broader savings picture without the tax question, the UK savings rates 2026 page has the gap between 1% and 4.5%.

Tax rules and rates change. Verify your current tax band and ISA allowance with HMRC or a qualified financial adviser before making decisions based on the numbers above. Editorial commentary, not personal financial advice.