How far back can an Income Support claim be backdated?

I have a clt who has been in receipt of IB since 2002.

He contacted us recently and we advised him he was eligible for an IS top up. He claimed this successfully and has been awarded a one month backdate. The clt said he did not know he was eligible for IS top up and therefore never claimed it.

How far back can he claim an Income Support backdate? Would he only get the three month backdate?

Technically, he should have been getting the IS top up since 2002 when his IB was awarded…however this was never included in his claim…He has never had any other income except for his IB….

My question is whether he could have been reasonable expected to know he was eligible for an IS top up and therefore expected to claim for it separately after he was awarded IB or is there a responsibility on the DWP to add the IS to the IB claim automatically?

No there isn’t.  Three months is the absolute maximum allowed by law on a wholly brand new claim and even then a statutory ground has to be made out.  If he can prove he was misadvised by the DWP, including a failure to advise where certain enquiries were made (one of the statutory grounds for the three month backdating by the way), then he should apply for an ex-gratia payment to cover the period.