I believe the landlord has fairly comprehensive appeal rights under the current regs, and that these probably do in fact include matters concerning how the o/p was caused:
Reg 3 of the DAR regs is clear that if recovery is sought from the landlord they are a “person affected”;
Reg 90 (1) of the 2006 HB regs is clear that any person affected gets a decision notice;
Reg 90 (2) states that any person affected “may request the authority to provide a written statement setting out the reasons for its decision [i:e81561a789]on any matter set out in the notice.[/i:e81561a789] (my emphasis)
Furthermore Schedule 9 para 15 (1) states that the decision notice that the landlord is entitled to (which he is therefore entitled to request reasons for, as above) must include, in subpara (b) “why there is a recoverable overpayment” and in subpara (d) “how the amount of the recoverable overpayment was calculated.
It seems to me that the policy intention is clearly that landlords should be able to dispute the detail of how an overpayment was caused and calculated, and that they can request relevant details – it does seem only fair.
I ought to declare an interest here – I work for a RSL!! 😉