Trade discounts allowed to customers may be deducted in ascertaining the amount to be reported as receipts from sales. Trade discounts include:
Discounts deducted from the face amount of the bill as a medium of adjusting the list price;
Discounts unconditionally deducted by customers upon settlement of their bills and allowed as a matter of established custom of a trade, without regard to the due date of such bills or to the form or terms in which such discounts are described or stated on bills or invoices. Discounts allowed to customers as cash discounts for prompt payment of their bills may not be deducted from receipts unless such discounts are taken at the time of sale.
Freight, delivery or other transportation charges may not be deducted from gross receipts except as provided in subsection (12):
If the seller contracts to deliver the property sold to some designated place, or is obligated under the terms of the contract to pay transportation charges to some designated place, the freight, delivery or other transportation charges so incurred by the seller may not be deducted from gross receipts.
If property is sold on terms requiring the seller to deliver such property to a designated place but the purchaser pays the amount of freight, delivery or other transportation charges in the first instance, and deducts such charges from the invoice price in making remittance to the seller, no deduction from gross receipts may be taken therefore by the seller.
Where the seller advances the freight, delivery or other transportation charges for the account of the purchaser in accordance with the terms of the contract of sale, such charges may be excluded from gross receipts provided:
That such charges are the actual charges incurred and are billed as such to purchaser, and
That the books and records of the taxpayer clearly indicate such facts.
Receipts from transactions in foreign commerce (as distinguished from interstate commerce) are excluded only to the extent such transactions may not be taxed under the provisions of the United States Constitution.