“The child now spends 4 nights a week with the claimant and partner”
so it seems the child is part of the customers household and should be included – child benefit only comes into play if 2 separate claimants want to have the kid included in their claim – at that point whoever gets the child benefit “wins”
but if theres no such dispute, and the child spends at least half their time with the claimant , i think the child should be included in the claim
