i filed i.tax return of my client from 6years from the PAN no which he told me & i saw his previous returns.but in this year i got that his PAN is wrong & that pan is also used by other assessee who is the actual owner of that PAN.my client brought form49 which he submit in incometax in 1994.i search his PAN as per form49 but no PAN found.if i apply new pan then any problem for my client? shall i give any letter to I.T.O. for my mistake?