(1)(a) Except as otherwise provided in this section or RCW 82.32.080, taxpayers owing tax under this chapter must file, on forms prescribed by the department, a return with the department on or before the date the taxpayer's federal income tax return for the taxable year is required to be filed.

(b)(i) Except as provided in (b)(ii) of this subsection (1), returns and all supporting documents must be filed electronically using the department's online tax filing service or other method of electronic reporting as the department may authorize.

(ii) The department may waive the electronic filing requirement in this subsection for good cause as provided in RCW 82.32.080.

(2) In addition to the Washington return required to be filed under subsection (1) of this section, taxpayers owing tax under this chapter must file with the department on or before the date the federal return is required to be filed a copy of the federal income tax return along with all schedules and supporting documentation.

(3) Each taxpayer required to file a return under this section must, without assessment, notice, or demand, pay any tax due thereon to the department on or before the date fixed for the filing of the return, regardless of any filing extension. The tax must be paid by electronic funds transfer as defined in RCW 82.32.085 or by other forms of electronic payment as may be authorized by the department. The department may waive the electronic payment requirement for good cause as provided in RCW 82.32.080. If any tax due under this chapter is not paid by the due date, interest and penalties as provided in chapter 82.32 RCW apply to the deficiency.

(4)(a) In addition to the Washington return required to be filed under subsection (1) of this section, an individual claiming an exemption under RCW 82.87.050(2) must file documentation substantiating the following:

(i) The fair market value and basis of the real estate held directly by the entity in which the interest was sold or exchanged;

(ii) The percentage of the ownership interest sold or exchanged in the entity owning real estate; and

(iii) The methodology, if any, established by the entity in which the interest was sold or exchanged, for allocating gains or losses to the owners, partners, or shareholders of the entity from the sale of real estate.

(b) The department may by rule prescribe additional filing requirements to substantiate an individual's claim for an exemption under RCW 82.87.050(2). Prior to adopting any rule under this subsection (4)(b), the department must allow for an opportunity for participation by interested parties in the rule-making process in accordance with the administrative procedure act, chapter 34.05 RCW.

(5) If a taxpayer has obtained an extension of time for filing the federal income tax return for the taxable year, the taxpayer is entitled to the same extension of time for filing the return required under this section if the taxpayer provides the department, before the due date provided in subsection (1) of this section, the extension confirmation number or other evidence satisfactory to the department confirming the federal extension. An extension under this subsection for the filing of a return under this chapter is not an extension of time to pay the tax due under this chapter.

(6)(a) If any return due under subsection (1) of this section, along with a copy of the federal income tax return, is not filed with the department by the due date or any extension granted by the department, the department must assess a penalty in the amount of five percent of the tax due for the taxable year covered by the return for each month or portion of a month that the return remains unfiled. The total penalty assessed under this subsection may not exceed 25 percent of the tax due for the taxable year covered by the delinquent return. The penalty under this subsection is in addition to any penalties assessed for the late payment of any tax due on the return.

(b) The department must waive or cancel the penalty imposed under this subsection if:

(i) The department is persuaded that the taxpayer's failure to file the return by the due date was due to circumstances beyond the taxpayer's control; or

(ii) The taxpayer has not been delinquent in filing any return due under this section during the preceding five calendar years.

Automatic expiration date and tax preference performance statement exemption—2021 c 196: See note following RCW 82.87.010.