A. If any amount of tax imposed or levied by any state tax law, or any part of such amount, is not paid before such tax becomes delinquent, there shall be collected on the total delinquent tax interest at the rate of one and one-quarter percent (1 1/4%) per month from the date of the delinquency until paid.

B. Interest upon any amount of state tax determined as a deficiency, under the provisions of Section 221 of this title, shall be assessed at the same time as the deficiency and shall be paid upon notice and demand of the Oklahoma Tax Commission at the rate of one and one-quarter percent (1 1/4%) per month from the date prescribed in the state tax law levying such tax for the payment thereof to the date the deficiency is assessed.

C. If any tax due under state sales, use, tourism, mixed beverage gross receipts, or motor fuel tax laws, or any part thereof, is not paid within fifteen (15) days after such tax becomes delinquent a penalty of ten percent (10%) on the total amount of tax due and delinquent shall be added thereto, collected and paid. However, the Tax Commission shall not collect the penalty assessed if the taxpayer remits the tax and interest within sixty (60) days of the mailing of a proposed assessment or voluntarily pays the tax upon the filing of an amended return.

D. If any tax due under any state tax law other than those specified in subsection C of this section, or any part thereof, is not paid within thirty (30) days after such tax becomes delinquent a penalty of ten percent (10%) on the total amount of tax due and delinquent shall be added thereto, collected and paid. However, the Tax Commission shall not collect the penalty assessed if the taxpayer remits the tax and interest within sixty (60) days of the mailing of a proposed assessment or voluntarily pays the tax upon the filing of an amended return.

E. If any part of any deficiency, arbitrary or jeopardy assessment made by the Tax Commission is based upon or occasioned by the taxpayer's negligence or by the failure or refusal of any taxpayer to file with the Tax Commission any report or return, as required by this title, or by any state tax law, within ten (10) days after a written demand for such report or return has been served upon any taxpayer by the Tax Commission by letter, the Tax Commission may assess and collect, as a penalty, twenty-five percent (25%) of the amount of the assessment. For purposes of this subsection, "negligence" shall mean the consistent understatement of income, consistent understatement of receipts or a system of recordkeeping by the taxpayer that consistently results in an inaccurate reporting of tax liability.

F. If any part of any deficiency is due to fraud with intent to evade tax, then fifty percent (50%) of the total amount of the deficiency, in addition to such deficiency, including interest as herein provided, shall be added, collected and paid.

G. All penalties or interest imposed by this title, or any state tax law, shall be recoverable by the Tax Commission as a part of the tax with respect to which they are imposed, the penalties bearing interest as provided in this section for the tax, and all penalties and interest shall be apportioned as provided for the apportionment of the tax on which such penalties or interest are collected.

H. 1. Whenever an income tax refund is not paid to the taxpayer within ninety (90) days after the return is filed or due, whichever is later, with all documents as required by the Tax Commission, entitling the taxpayer to a refund, then the Tax Commission shall pay interest on the refund, at the same rate specified for interest on delinquent tax payments. The payment of interest on refunds provided for by this section shall apply to tax year 1987 and subsequent tax years. The Tax Commission shall not be required to pay interest on an income tax refund which is applied, in whole or in part, to a prior year tax liability pursuant to Section 2385.17 of this title or upon an income tax refund applied, in whole or in part, to satisfy a debt owed to the Internal Revenue Service of the United States or to a state agency, including the Oklahoma Tax Commission, as provided by Section 205.2 of this title.

2. For tax returns filed after January 1, 2004, and before January 2, 2010, whenever an income tax refund is not paid to the taxpayer within the following number of days after the income tax return is filed with all documents as required by the Tax Commission or after the income tax return is due, whichever is later, entitling the taxpayer to a refund, then the Tax Commission shall pay interest on the refund at the same rate specified for interest on delinquent tax payments:

a.for returns filed electronically, thirty (30) days, and

b.for all other returns, one hundred fifty (150) days.

3. For tax returns filed after January 1, 2010, whenever an income tax refund is not paid to the taxpayer within the following number of days after the income tax return is filed with all documents as required by the Tax Commission entitling the taxpayer to a refund, then the Tax Commission shall pay interest on the refund at the same rate specified for interest on delinquent tax payments:

a.for returns filed electronically, forty-five (45) days, and

b.for all other returns, ninety (90) days.

Added by Laws 1965, c. 414, § 2, emerg. eff. July 7, 1965. Amended by Laws 1983, c. 13, § 1, emerg. eff. March 23, 1983; Laws 1988, c. 87, § 1, operative July 1, 1988; Laws 1988, c. 204, § 9, operative July 1, 1988; Laws 1989, c. 249, § 9, eff. July 1, 1989; Laws 1990, c. 339, § 12, eff. July 1, 1990; Laws 1991, c. 342, § 8, emerg. eff. June 15, 1991; Laws 1993, c. 146, § 8; Laws 1998, c. 385, § 2, eff. Nov. 1, 1998; Laws 2003, c. 472, § 5; Laws 2004, c. 535, § 1, eff. Nov. 1, 2004; Laws 2009, c. 156, § 1, eff. Jan. 1, 2010; Laws 2014, c. 274, § 1, eff. Nov. 1, 2014; Laws 2016, c. 28, § 1, eff. July 1, 2016.