Low earners are able to earn interest on savings without paying tax up to the personal allowance plus the £5000 starting rate.
Based on savings interest alone a maximum of £17500 tax free interest is available if that is a persons only income source.
This figure is reduced by other income.
Somebody earning £17000 by PAYE would only get £500 tax free starting rate.
Adding in the Personal Savings Allowance for interest of £1000 means that in practice the maximum interest only income tax free is £18570.
This is separate from an ISA which is tax free.
You need to register for self assessment if your income from savings is above £10000.
Savings income above £10000
Self assessment
eg. Savings income £10000
PAYE income £8570.
No tax to be paid, personal allowance use is £4000, £5000 starting rate, £1000 PSA.
So tax is paid on total income - personal allowance - starting rate - PSA (£18570)
eg. Savings income £10000
PAYE income £10000
Tax to be paid on £20000-£18570=£1430.
eg. Savings income £11430
PAYE income £8570
Tax to be paid on £20000-£18570=£1430