Tonnage tax option requires separate ship accounts and an accountant's report before the return filing deadline to be effective. An option for the tonnage tax scheme will not take effect for a previous year unless the company maintains separate books of account for operating qualifying ships and furnishes, with the return of income for that previous year, an accountant's report in the prescribed form duly signed and verified; Form No. 66 must be furnished at least one month before the return due date and non compliance renders the option ineffective for that previous year.