Reclaiming overpayment of CIS for Ltd Company

A new client has come to us and upon completing the first set of accounts we've found that there has been CIS tax that was due back, but has never been claimed by the previous accountant, for the last 6 years.

The only way of reclaiming the tax, that I know of, is to submit P35s but as they would now be late (a PAYE scheme was never set up by previous accountant as there were no salaries) I am thinking that the openalties would outweigh the tax refund.

Does anybody know of another way of approaching this?

Thanks in advance to all who can assist.