Section 280-RICR-20-55-2.5 - DefinitionsA. "Proper estimate" means a Rhode Island extension form filed by the regular due date which declares at least eighty percent (80%) of the tax due for the taxable year.B. "Reasonable cause" means a taxpayer exercised ordinary business care and prudence and was nevertheless unable to file the return within the prescribed time.C. "Regular due date" means the fifteenth day of the fourth month following the close of a taxable year (for calendar year filers this would be April 15th).D. "Rhode Island extension," for purposes of this regulation, means Form RI-4868 or Form RI-8736, whichever is applicable.E. "Willful neglect" means a conscious, intentional failure or reckless indifference or failure to exercise ordinary business care and prudence.280 R.I. Code R. § 280-RICR-20-55-2.5