2005WL mearns

My wife pays no income tax as her only income is her State Pension of £5374. This has allowed her to arrange a Marriage Allowance Transfer to me. She does have savings that currently generate over £5000. I realise she can use the Starting Savings Allowance of £5000 and Personal Savings Allowance of £1000 meaning no tax would be due. However I believe where income is below the Personal Tax Allowance of £12570 the difference between this and the income, can be added to the tax free savings allowance. This allows savings interest of more than £6000 to be untaxed. For example using my wife’s figures: Personal Allowance £12570 Less: Income (State Pension) £5374 Marriage Allowance Transfer. £1260 (minus) £6634 Leaving Personal Allowance (equals) £5936 Add: Starting Savings Allowance £5000 Personal Savings Allowance. £1000 (add) £6000 Amount of savings interest tax free £11936 Am I correct? At what stage would a tax return be required? I would welcome advice and thank you in advance. Apologies, but I was unable to complete the maths in any other way!

My current income is my state pension of £5374 and savings interest projected to be £6700.00. What is the maximum savings interest I can receive in 2024/2025 before being liable to tax? Any help much appreciated.