Another pay question - employing part time

[deliakate]

So if I employed a mother's help for approx 15 hours per week, she would presumably have another job too for the rest of the time. DH thinks this would mean that we and the other employer would effectively be sharing her, and have to share the tax/NI burden etc. Can anyone confirm or deny? Thank you

IF she has another job you should both share the burden - form P46 - which you can get online from the HMCE website - can be filled in, with a covering letter to the area tax office stating that she wants to have a personal allowance split between her 2 employments - she could work out how this would be beneficial so she does not waste any personal allowance - i.e. 50/50 split,
or 60/40 etc.
as regards national insurance that is not shared and is individual to each job

You should agree a Gross salary. Then you deduct Employee tax and NI as per her taxcode, which could be BR if using the entire personal allowance in another job.

Have a play with calculator.kistax.com and try varying the taxcode. 647L, BR

Would be up to her if she wanted tax code split between jobs, not for you to determine as the employer in my view. So by agreeing a Gross salary, tax code changes do not make a difference to your overall cost. Instead it makes a difference to how much you deduct from their earnings to send to HMRC.