Sorry this is a bit late, only just found the thread.
The fact that they have added the word "Bill" makes no difference at all unless it conforms to the requirements of a bill of exchange.
I could give you a bit of paper with the word bill written on it and an arbitrary amount i wanted you to pay me.
Would it be a bill?
Would you have to pay it?
Not unless you and I have a prior agreement that I can bill you for my services (A bill of Exchange or Contract) that has both our signatures on and I have given full disclosure of exactly what I am going to be billing you for and not hiding any hidden extras, and we both put something of value up front that neither of us would like to loose should the other find us cheating in our agreement.
From then on any bill I give you must have my wet ink signature on it and a description of what service I have carried out for you, then it can be called a bill.
That's what constitutes a bill (in my opinion) if anyone would like to add to that, or correct me then feel free.
A stork, A pelican, The Tax Man. Have one thing in common? They can all stick their bills up their arse!
"I would have invaded Iraq anyway" Tony Blair, War Criminal and EU Paid Traitor!