Period of turnover determination: turnover periods follow state return periods; default quarterly periods apply for non-filing dealers. Determination of turnover follows the period for which a dealer must submit returns under the appropriate State general sales tax law; if a dealer is not required to submit such returns, the period of turnover defaults to quarterly periods ending 30 June, 30 September, 31 December and 31 March in a financial year. A former, now-omitted provision set out specific deductions from aggregate sale prices, including a formula for extracting tax included in sale prices and adjustments for goods returned within three months with satisfactory evidence.