£300,000 Savings at 4.5% — Tax on Interest 2025-26
Annual interest earned: £13,500 · Personal Savings Allowance applied
Tax breakdown — £300,000 savings at 4.5%
| Taxpayer band | PSA | Taxable interest | Tax owed | Net interest |
|---|---|---|---|---|
| Basic rate (salary ≤ £50,270) | £1,000 | £12,500 | £2,500 @20% | £11,000 |
| Higher rate (£50,270–£125,140) | £500 | £13,000 | £5,200 @40% | £8,300 |
| Additional rate (over £125,140) | Nil | £13,500 | £6,075 @45% | £7,425 |
Frequently asked questions
How much tax do I pay on interest from £300,000 savings at 4.5%?
Interest earned: £13,500/year. Basic rate taxpayer (salary under £50,270): tax £2,500, net interest £11,000 — the first £1,000 is covered by your Personal Savings Allowance. Higher rate taxpayer (salary £50,270-£125,140): tax £5,200, net £8,300 (PSA is only £500). Additional rate taxpayer (salary over £125,140): no PSA, tax £6,075, net £7,425.
What is the Personal Savings Allowance for 2025-26?
The PSA allows basic rate taxpayers to earn £1,000 in savings interest tax-free per year, and higher rate taxpayers £500. Additional rate taxpayers (over £125,140) have no PSA — all interest is taxed at 45%. ISA interest is always tax-free and does not count toward the PSA.
At 4.5%, what balance triggers a tax bill for a basic rate taxpayer?
A basic rate taxpayer's PSA covers £1,000 of interest. At 4.5% interest, this is used up at a balance of £22,222. With £300,000 at 4.5%, your interest is £13,500, so you exceed the PSA by £12,500, which is taxed at 20%, giving a bill of £2,500.
Should I put £300,000 in an ISA or savings account?
A cash ISA pays tax-free interest regardless of your tax band. A regular savings account uses your PSA first (but at 4.5% on £300,000 you earn £13,500, exceeding the basic rate PSA of £1,000). If you are a higher or additional rate taxpayer, an ISA is more valuable. Basic rate taxpayers may not benefit from an ISA if interest stays within their £1,000 PSA.
Do I need to declare savings interest on £300,000 to HMRC?
If your total savings interest exceeds your Personal Savings Allowance (£1,000 basic rate / £500 higher rate / nil additional rate), you must declare the excess to HMRC. At 4.5% on £300,000, your interest is £13,500/year. This exceeds the basic rate PSA, so basic rate taxpayers pay tax on £12,500, and higher/additional rate taxpayers owe more. HMRC may collect this via PAYE coding or Self Assessment.
How much will £300,000 grow to in 5 years at 4.5%?
With compound interest at 4.5% per year, £300,000 grows to approximately £373,855 after 5 years and £465,891 after 10 years (before tax). Each year you earn roughly £13,500 in interest, which then compounds. If you are a basic rate taxpayer, the after-tax interest is £11,000/year, giving a net compound balance of approximately £359,184 after 5 years.