Change of circumstances - is UC claim needed?

I am advising a grandmother who is bringing up two grandchildren. She lives in a UC full service area. The younger child is about to turn 5 .  The grandmother is currently claiming Income Support and has been told she’ll have to claim UC when the child is 5.  She is a couple of years off pension age and is very worried about having to be available for and search for work.  She receives a Special Guardianship allowance from social services for the grandchildren, and she has decided that she can manage to live on that, as long as she can continue to receive HB and CTC. (ie She can manage without the UC basic allowance).  My question is whether she will be able to continue to claim HB (and CTC) when her IS claim ends, or will she have to make a UC claim? As it will only be a change of circumstances, rather than a new claim for a legacy benefit, I am assuming it will be the former?

Yes so long as she already had claim in for housing benefit and CTC she can continue to claim them - she needs to make sure the HB doesn’t lapse when the IS stops so, as you say, she will need to notify change of circumstances.