Presumptive taxation for mineral oil services applies to non-residents, with lower-profit claims tied to books and audit compliance. Special presumptive computation applies to non-residents providing services, facilities, or plant and machinery for prospecting for, extraction or production of mineral oils. Income is computed at 10% of specified receipts, contrary general provisions do not apply, and the assessee may claim lower profits only by maintaining prescribed books and furnishing the required audit report. No separate deduction is allowed, depreciation is deemed to have been claimed and allowed, and certain technical service receipts are excluded from the scheme.