UNDERPAID TAX

A potential new client has contacted me to help sort an existing tax problem. Apparently he has, following a conversation with a fellow employee, contacted the Revenue to advise he thought he was being undercharged tax. He has 2 employments, but neither PAYE code reflected this, the second only charging hime at basic rate. Unfortunately, he was correct in his belief; the Revenue has now investigated his file back to 2002/03 I believ, and is now demanding payment of overdue tax of £6000 within 30 days. I will be meeting the client next week, and will obviously be doing my own research b4 the meeting and following the meeting if I feel I can assist in this matter. In the meantime I would be very grateful for any opinions or details of potential sources regarding the following:

1. Is it reasonable for the Revenue to go back in this way, as earnings have been reported to them by the 2 employers throughout.
2. If so, is it reasonable for them to insist on payment over such a short timescale.

The client is obviously worried about finding the funds over such a short timescale, and feels he is punished for being honest; many would not have contacted the Revenue, and given this has been going on for several years, they may never have been picked up by them. Indeed, if he had not spoken to another employee, he would not have even known there was a problem; he had previouslyassumed all tax was being collected through his PAYE.

Any assistance regarding myquries, or anything I have not considered at this stage.
Stephen Davies