Starting Savings Rate

All the examples I have seen of the Starting Savings Rate explain what will happen only when the Earned Income is less, equal or greater then the relevant allowances. I want to know what happens when someone has more savings interest after all the allowances are used up. Is only the excess of taxable savings taxed, or would one loose the £5K Starting Savings Rate altogether? For clarity, here is an example: Someone whose only Earned Income is a New State Pension and, say, £20,000 in taxable savings interest? Other examples would be someone in the same Earned Income situation but with £10k or £15K of taxable savings interest. Thanks for any enlightenment.

Your allowances for earning interest before you have to pay tax on it include:

your Personal Allowance
starting rate for savings
Personal Savings Allowance
Please see the guidance at:
https://www.gov.uk/apply-tax-free-interest-on-savings

If you earn interest over your allowance but under £10,000 and are employed or receive a pension, HMRC will change your tax code so you pay the tax due automatically.
The code for the current year will be based on how much interest you had in the previous year.

You need to register for Self-Assessment if your income from savings and investments is over £10,000 in the financial year.
You can find further information here:
https://www.gov.uk/check-if-you-need-tax-return

Tax on savings interest: How much tax you pay - GOV.UK (www.gov.uk)

The simplest option would be to just fill in the online tax return with such a case, and see what it calculates. An alternative option would be to look at the Notes document that explains the SA110 Tax Calculation Summary form used in paper tax returns. The Notes document includes an elaborate workings sheet (the notes run to 53 pages). On page TCSN 13 of the notes, it seems to be suggesting that the starting rate band size is limited only by the amount of non-savings income - but I didn't spend that much time chasing references around the various numbered boxes.

Sorry it's taken so long to respond. Thank you maxb for trying to help. I got a copy of the page you cited. Unfortunately I'm not yet any wiser. I just find it highly suspicious that it seems impossible to get a straight answer from HMRC. Anyway, thanks again.

In this scenario, if your pension is below your personal allowance, you are entitled to the starting rate of savings. Only earned income ( which includes pensions) is taken into account. Savings interest is considered separately . Fir example, if you have a tax code of 12500, pension of £1000 and savings interest of £20000, you are entitled to the starting rate of £5000. So of your £20000, you get £5000 exempt from tax, plus £1000 exemption fi4 your personal savings allowance. As your pension leaves £2,500 spare in your tax code, you are exempt from a further £2500 there. So in this hypothetical situation, your £20000 savings interest is only subject to tax on £11500 ie 20000-5000-1000-2500), at you normal rate (29%) so you’d owe HMRC £2300 in tax on interest received. As your interest recieve dis in excess of £10000, you need to complete a self assessment form, and the tax will fall due the following January in you file electronically.