sportyfae

You can only ever get tax relief for the tax year the pension contribution is paid in. All that carry forward enables you to do is contribute more in a later year, it's still a contribution of the later year not the year you have carried forward the unused annual allowance from. I'm not aware of any exceptions for TFC which would alter that basic principle.

Yes you are mistaken. It's taxable and is taxed. But the first £500 is taxed at 0%. It still forms part of your adjusted net income so can increase your overall tax liability even if taxed at 0%.

"Your pesonal allowance, if due, can then cover any of the income that is above the savings or dividends allowance". Pretty sure that is wrong. It is only when you have used your Personal Allowance can the savings and dividend rate bands (aka savings starter rate, PSA & dividend allowance) be used. You can't use them and then your Personal Allowance.

No, receipt of Marriage Allowance entitles you to a fixed tax deduction off your overall income tax liability, not any extra allowances. If your non savings non dividend income is £15,000 then the savings starter rate available will be £2,570. Once that has been used you can start to use the savings nil rate (aka Personal Savings Allowance). Your tax liability will be reduced by £252 from the Marriage Allowance tax deduction (£1,260 x 20%). It is different for your wife, by applying for Marriage Allowance she has a reduced Personal Allowance of £11,310.

Yes, the savings nil rate of tax (aka PSA) is for a tax year. If you earned say £900 in interest then that would be taxed at 0%. If you earned £1200 then £1000 would be taxed at 0% and £200 at 0%. The above assumes you are paying enough basic rate tax on your job/pension income to not have any savings starter rate band available.

Are the 3 years creating the discrepancy starting credits? From NIM41210 - Credits: post 1975 credits: Class 3 starting credits These starting credits could be awarded for the full three tax years containing their 16th, 17th and 18th birthdays, whether or not the young person was in full time education,