Guest staying and council tax?

[LeoandBoosmum]

Hi, I am currently living with my mother and she works part time. I am an adult but unable to work right now due to illness. I am not therefore able to live alone. I have a best friend who is going to be renting a house locally and will, being alone, be eligible for the 25% council tax reduction. My best friend, who knows things are often tense at home because my mother is not always understanding of my condition, has said I can visit/ stay with them regularly as long as they are not acting illegally and won't have their CT discount invalidated.
We would both like to act within the parameters of the law (I do not want to get my friend into any trouble but appreciate their offer to rescue me from a sometimes intolerable situation) and wondered if any one knew the rules surrounding this? How often can a guest stay? For how many days at a time, over a week or month, for example can I be a guest at my friend's rented house before the council tax discount is breached? My friend's tenancy is for 6 months.
As I have said, I am not planning on moving in with my friend by any means, but I'm concerned that if I unwittingly stay for longer than allowed at a time or the local council visits to check out the validity of my friend's claim and sees my things there from staying over, my friend may get into trouble. I am also concerned neighbours may report my being there too often (to the landlord or council) so, while I appreciate my friend's offer, I don't want to break the rules and bring trouble to myself and them.
I looked on the local council's site and found nothing... Any one know?

I mean to add, thanks!

In a previous life I managed a Council Tax department.

Basically, occupancy is determined on whether a property is your "sole or main residence". Therefore, while you are living with your mother (and she is not claiming to live alone and get the single occupier discount of course) and your possessions, belongings, your post etc... are at your mother's address it's unlikely that you could be considered resident with your friend.

There is no set amount, or percentage, of time that determines residency though so it can be queried. If it is ever queried it would help your case if you could prove that you are paying your mum some rent or contributing to bills at her house.

HTH

I also used to work in council tax & wholeheartedly agree with Waspie

If your Mum is paying full charge for ctax for herself & you as the 2 adults at the property, then this is classed as your sole & main residence.

No matter how often you stop at your friend's house, she would still be charged 75% of the full council tax bill.

Thank you both very much. That is really helpful and I appreciate your taking the time to respond, especially given your expertise.