it's all complex with ftb and csa. if he was having the kids 50/50 then yes, he is definitely entitled to FTB (dependant on his income - he may not get the same amount as the mother). CS would be calculated by taking into account the amount of time he has the children, his income, her income etc. it's not a simple calculation.

if he has previously agreed to have money deducted from his wages for CS, any arrears would be added to that as money he owes. my guess is that she has contacted them to say that he no longer has the children at all from X date, so the amount of CS has increased based on him not having care of them

does he have a court order/parenting plan in regards to their arrangement (50/50 time)? if not, he needs to attend mediation to arrange a parenting plan so that there is a WRITTEN agreement in regards to shared care. for one, it allows him to claim the FTB that he is entitled to. for another, it stops her being narky and witholding care from him for whatever reason. he can contact the Family Relationships Advice Line for info on this. you can contact on his behalf for advice too - but can't make appointments etc. if he arranges mediation and she doesn't attend, he can go to court and get court orders in place for care as she hasn't attended mediation and stuff.

in the mean time - contact FAO re shared care. he should be claiming FTB for the time he has the kids. he can claim retrospectively if he wishes - he'll have to provide a diary showing what nights he has had the kids in care. if he does this, and she has been claiming 100% care, a debt will be raised against her. a lot of people won't do a retrospective claim to keep the peace - but he IS entitled to it so can do it if he wants. make sure he keeps a diary of all the time the kids are in care. any contact he has had with her in regards to care (so he was supposed to pick them up at x time but she contacted to say he couldn't and things like that)

contact CSA to query HOW the arrears came about. was it because of a shared care issue? or was it because his income is higher than he'd estimated and he now owes extra. get that sorted out. if he is a little wary of dealing with these offices, he can ring up and identify himself and get you to speak to understand it a bit for him. i have done this with family to help them out

if the extra payment is going to leave him in financial hardship being $40, then he needs to say something and see if he can negotiate a smaller repayment over a longer time.

hope that helps

BG