The overall verdict from that friend of mine was more a series of questions: Does the child in question claim Income Support and DLA himself, as well as he mother claiming Income Support and Housing Benefit? The paper doesn't make this clear, but if the answer was no then that would be the way of solving their problem, as the total sum of money he should be entitled to individually is just short of £230 a week -- plus any income support for the mother (= approx. £100 a week), plus the Housing benefit that is taking the hit. So that's £330 a week of money that they could potentially be receiving that the story hasn't accounted for -- out of that it ought to be just about possible to re-budget and squeeze £20 a week.
This change is short-term as Housing Benefit is shortly to be replaced by UC, and I quote: "I guess the theory is that any dependants or non–dependants are cared for by the parents, so they shouldn't need an overnight carer. This of course ignores the need for respite for the carer, and it may not be possible for this to be provided by putting the disabled person in a hospice, rather than having an overnight carer. At the moment councils can make discretionary payments, but that doesn't seem to have been duplicated for UC."
So, assuming that the family is claiming all they are entitled to at the moment, problems like this could easily get more common in future.
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Shar, to answer your question: The income rules for HB are very obscure, and my contact hasn't worked on them "since 1988", so doesn't know. But she suspected that no, it shouldn't make a difference. So if someone wanted to gift money and cover the shortfall for this woman then there probably wouldn't be a problem with that. I would still probably advise the woman in receipt of the gift to declare it, but there oughtn't be any issue. The only problem might be if her income is almost at the threshold beyond which HB stops being paid, but it's highly unlikely that £80 a month will tip her over that.