Okla. Admin. Code § 710:65-19-75
Persons conducting recreational events occasionally assert that the receipts are not taxable because they are donations and not charges for admission or an item of tangible personal property. To qualify as a donation, a payment must be totally voluntary and no restriction whatsoever may be placed on the entrance or receipt of tangible personal property of persons not making a donation. The facts surrounding the request for the donation must be obvious that admittance or receipt of property is not restricted to those making a donation. A set amount for the donation (through newspaper publicity or signs at the entrance), a turnstile or restrictive device that must be passed through, denial of tangible personal property or an attendant requesting a donation at the door shall be presumptive evidence that the charge is not a donation but that the payment is required. [See: IRS Revenue Rule 67-246]
Okla. Admin. Code § 710:65-19-75