Okla. Admin. Code § 710:1-3-45
The following words and terms, when used in this Part, shall have the following meaning, unless the context clearly indicates otherwise:
"Involuntary payment" means any payment received by the Commission as a result of or in connection with any distraint, levy, seizure, attachment or garnishment, or any other legal proceeding or administrative action wherein the Commission seeks to collect or enforce the collection of a tax liability or to file a claim therefor. Such proceedings and actions include, but are not limited to, bankruptcy proceedings, the filing and forwarding of tax warrants directing the levy and sale of property, and any administrative action or proceeding wherein the Commission proposes to revoke, cancel, suspend or deny any license, permit or privilege because of an outstanding tax liability. Payments made pursuant to an installment or "payout" agreement entered into as a result of or subsequent to the institution of any of the above collection measures are deemed involuntary payments.
"Liability period" means the reporting period of a delinquent tax or tax liability, or, in the case of tax liabilities determined as a deficiency, all reporting periods included in the assessment of such deficiency. For purposes of determining the earlier of two or more liability periods, the beginning date of each liability period is used.
"Partial payment" means any payment to or receipt by the Commission of an amount less than sufficient to pay in full all tax liabilities of the taxpayer.
"Tax liability" means delinquent taxes and tax amounts determined as a deficiency, and includes all penalties, interest, service charges and fees accrued and accruing in relation thereto.
"Voluntary payment" means a payment made prior to or in the absence of any legal proceeding or administrative action in or by which the Commission seeks to collect or enforce the collection of a tax liability. Payments made pursuant to an agreement voluntarily entered into between the taxpayer and the Commission prior to such legal proceeding or administrative action will continue to be deemed as voluntary payments only so long as the taxpayer remains in full compliance with the terms of such agreement.
Okla. Admin. Code § 710:1-3-45