deduction from earnings - not taken into account for UC payment

I’ve been trying to find something that helps with this query but no luck - I have a client who had a wages arrestment direct from her wage, UC have not taken this into account.  In their calculation they have used an income of £1238.96 when in actual fact after the wages arrestment it was £1095.49. 

is this right?

Only specific deductions from earnings are taken into account under UC. Deductions for debts are not on this list.

I do actually get the logic on this one. If it was taken into account, then someone who is having a debt deducted from their wages would be better off than someone who was paying the creditor themselves because they would get some of the deduction back via UC.

Yes very true, the more I was thinking about it I can see why it would make sense to take the full earned income into account.  Thanks.