Haw. Rev. Stat. § 231-36.8

(a) If a claim for refund or credit with respect to tax is made for an excessive amount, the person making the claim shall be liable for a penalty in an amount equal to twenty per cent of the excessive amount; provided that there shall be no penalty assessed where the penalty calculation under this section results in an amount of less than $400.

(b) It shall be a defense to the penalty under this section that the claim for refund or credit had a reasonable basis. A person claiming the reasonable basis defense shall have the burden of proof to demonstrate the reasonableness of the claim.

(c) This section shall be construed in accordance with regulations and judicial interpretations given to section 6676 of the Internal Revenue Code.

(d) For purposes of this section:

"Excessive amount" means the amount by which the amount of the claim for refund or credit for any taxable year exceeds the amount of the claim allowable for such taxable year.

"Reasonable basis" means a standard of care used in tax reporting that is significantly higher than not frivolous or not patently improper. A reasonable basis position will be more than arguable and based on at least one or more authorities of either state or federal tax administration. A position is considered to have a reasonable basis if a reasonable and well-informed analysis by a person knowledgeable in tax law would lead that person to conclude that the position has approximately a one-in-four, or greater, likelihood of being sustained on the merits. A reasonable basis includes innocent mistakes where the excessive amount is the result of inadvertence, mathematical error, or where otherwise defined as innocent by the director pursuant to a formal pronouncement issued without regard to chapter 91.

(e) This section shall not apply to any portion of an underpayment on which a penalty is imposed under section 231-36.6. [L 2009, c 166, §3; am L 2012, c 185, §1]