You don't half.
When I was working, the office went over from Tax Credits Helpline to Debt Management.
We dealt with PAYE, VAT, SA, CT and Tax Credit Debt.
No single person can handle the intricacies of them all, so you were allocated two, I had TC and PAYE*.
With TC debt, one of the things you did was an income and expenditure assessment. The first time someone told me they were paying £70 a month for water, I nearly fell off my chair. I did come across the odd one that was higher than that. As you can see from the bill above, we pay £31.01.
*Even now, when an advert for Sage accounting software comes on TV my blood pressure rises. These fuckers gave us a lot of unnecessary work. The fucking dimwits software couldn't recognise five week months, and directed the payment into the following month. Our software was and and still is utter crap, so moving money from one month to another took about ten minutes. Short staffing meant that six months of payments could be in the wrong place before we contacted them.