Need to be clear that
- backdating is what you get if the date of claim is backdated to before the actual date of claim.
- arrears is what you get if you are paid back to the date of claim. Not the same as backdating at all.
Also be aware that the tribunal do not have to award from the date of claim at all. They can award from a subsequent date if that's when they believe either that the backwards test was first satisfied, or, from the date a supersession was applied for. It's a blank slate on most aspects under appeal unless argued and agreed otherwise.