Working from home tax relief

[Motiv]

I'm just helping my mother-in-law with trying to claim tax relief relief for working from home.
Its just a little bit more complex because she's PAYE and self employed.
The majority of her income is PAYE, but she does some private work in the evenings. She fills in a self assessment each year.

Does anyone know if she can use the microservice, as she is claiming for tax relief from her employer rather than for her private work.

Or doesn't it work like that?

Martin Lewis says if you fill in a self assessment you can't use it, but I want to check as its to do with her employer rather than her self employed work.

Can anyone help?

Thanks in advance
 

[Playing with Fire UK]

I'm not certain about the micro service, but the place to put it on the tax return is in the employer section, called something like work expenses that haven't been reimbursed. The tax return includes information about both the self employment and the PAYE income - you do one per person, not per employment.

[MisterA]

I'm employed, but have used the microsite. Its really easy to use, just follow the link and fill it in, it's self-explanatory. It won't allow you to proceed, if you're not able to use it:
https://www.gov.uk/tax-relief-for-employees/working-at-home