Section R. 207.124 - Tax determination; discountsRule 4.
(1) A cash, trade, or quantity discount shall be deductible in arriving at the charge for the transaction subject to the excise tax. Such a discount shall appear on the invoices, records, and accounts of the person engaged in the business of providing an airport parking facility and shall be substantiated to the satisfaction of the department. Such a discount may be allowed as a deduction on a return filed with the department when there is sufficient evidence in the business records to indicate that such a discount has been a regular policy and has been given to a customer.(2) A trade or a quantity discount shall be deductible immediately on the invoice before determining the tax.(3) A cash discount shall not be deducted by the person engaged in the business of providing an airport parking facility until the customer has received the discount and paid for the transaction.Mich. Admin. Code R. 207.124