Gross receipts for section 44ada of income tax act

Newly inserted Section 44ADA now offers presumptive taxation to certain professionals. Under the section, income is to be presumed at 50% (or above) of gross receipts if the same do not exceed Rs.50 lakh. A professional generally follows cash-basis when accounts are to be maintained. But now if he opts for Section 44ADA, accounts are not required to be maintained. Under the situation, a question arises whether if he so opts S.44ADA, should the gross receipts be considered on "cash basis" or "accrual basis". I shall be grateful if the learned readers offer view on this aspect.