Backdate of underpaid benefit

Scenario : Client on nil income ESA but conts being paid due to working partner.

Working partner falls out of work, so she calls them to get benefit reinstated.

Benefit amount reduced by 90 quid a week, as there was a 4 week run on of WTC.

6 months later benefit still reduced by 90 quid a week.

DWP say she has to prove they arent getting working tax creds. If he was getting WTC then he would have to work 30 hours a week to qualify for them, and his wages + TC would wipe out her ESA in full anyway?

Also it was clearly explained by DWP when claim was made last year that their benefit would reduce due to the run on.

As far as i know the DWP have overlooked this, and are trying to blame everything on the claimant, even though she gave DWP a full explanation of their circumstances when the claim was put back into payment in November.

I think the amount paid should be revised and backdated, as i think its official error here. All material facts disclosed
but DWP didnt act on it perhaps?

What are my chances of getting this underpaid benefit paid to them? Theyve been living on £160 a fortnight and are in a financial mess. Arrears would solve many problems!

Thanks

“I think the amount paid should be revised and backdated, as i think its official error here. All material facts disclosed
but DWP didn’t act on it perhaps?”

Only decisions can actually be revised for official error, and presumably the only decision was the one to award ESA in the first place. It is certainly arguable, but it depends very much on DWP themselves accepting that the decision did indeed arise out of official error. There is no right of appeal against the refusal to revise for official error. Arguably a better avenue would be to write in requesting late revision of the decision (what would be termed a late application for mandatory reconsideration), whilst suggesting revision for official error at the same time. I don’t know what your experience of late MRs has been, but the DWP have been pretty ready to accept late MRs in the cases we have put forward. If they accept the late MR application but do not change the original decision, you would get a right of appeal