I have always understood, without ever really needing to know why, that the SoS must produce at appeal a copy of the decision under appeal. Can anybody point me to an appropriate act/reg/CD please?

In this case the client is appealing an IS overpayment. The SoS submission included the overpayment decision, but a strip at the right hand side of the page was missing. The tribunal chairman adjourned the hearing and directed the SoS to produce a "proper" copy. They provided exactly the same document with the missing words (which turn out not to be critical but could have been almost anything) hand written in, and no form of certificate to verify that it is as per the original, which presumably can be seen but not fully printed on the DWP computer.

Under s 71 it is a necessary prerequisite of recoverability in any overpayment case that the previous decision awarding benefit has been either revised or superseded (so as to remove or reduce benefit for the relevant period)and the SoS needs to prove this. Failure to revise or supersede before issuing an overpayment decision means that any overpayment found is irrecoverable. However it doesn't stop them having another go and getting it right...

There have been decisions (I’ve forgotten the references) stating that it is sufficient to produce a computer printout showing the terms of the decision. However, notwithstanding that, R(IB) 2/04 makes it clear (without expressly saying so) that as long as there is evidence of a revision or supersession having been made under sections 3 or 10, then there is no need to produce the original decision as the tribunal has the power to reconstruct it or correct any defects in it.

Those old arguments, which we all used to relish, about producing original decisions and tribunals not being able to correct defects in the DWP’s reviews are (except in rare cases), unfortunately, things of the past. IT and the Social Security Act 1998 saw to that.

That should read "sections 9 or 10".

As noted by nevip, it is not necessary to prove a decision with every single piece of documentation. If there is reasonable evidence to show a decision was made, that is sufficient. Anecdotally from discussions with LA POs, Tribunals appear to be much less fond of this type of argument.

There are several CDs where evidence of a decision has been at issue. Some have been found against LAs, but the majority have, more or less, taken a view that is reflective of observations made by Cmmr Jacobs in CH/2349/2002. He suggested that LAs were not required to produce something akin to a "...detective novel..." (paras 6-9, 12).