Offset Personal Allowance against earned interest?

Hello, I have already read the "Tax on savings interest" webpage and think it says that interest earned on savings in addition to the £1000 "Personal Savings Allowance" can be offset against the "Personal Allowance", providing one hasn't already used the "Personal Allowance" on wages, pension or other income. Can I check that this conclusion is still the case given the following? My wife and I have a joint account. I work full time and my salary is paid into the account. My wife does not work due to being a stay at home mum/housewife. If she earns interest in an account in her name with, for example, money from our joint account or an inheritance, will the interest earned still be offset against her "Personal Allowance"? Thanks in advance . 

Name removed admin .

Hi Ians,
Joint interest is by default split 50/50 between spouses and civil partners.
The alternative is a split based on beneficial ownership of the interest.
This is made using form 17 and a declaration of trust, both of which, are submitted to HMRC withing 60 days of the form 17 being signed.
If your wife's income, including interest is below £17570, then she is entitled to claim her Personal Allowance and up to £5000 starting rate for savings.
Thank you. 
 

Hello, Thank you for your reply but there's a couple of things I still haven't understood/am confused by. 1) Where is joint interest applicable if interest is earned on, for example, a fixed term savings account in my wife's name only? Does it have anything to do with where the capital to invest comes from? 2) I don't see the relevance of Form 17 as this appears to be for income from a property that's in a joint name and my original question mentioned nothing about a property? In a nutshell the question I am asking is if my wife can claim her Personal Allowance (£17570) against any interest gained (on a fixed term savings account in her name only) such that it's tax free, given that she has no income at all due to being a stay at home mum? Is it relevant where the capital she would use comes from? Thanks again in advance.

Hi
1. for joint accounts it is 50/50  2. the form 17 is for income in joint names and not just property. You would still need this to change the split on the joint interest account. Your wife will be entitled to the £17570 you refer to for income in her name only.