Section 280-RICR-20-25-10.18 - Estimated TaxA. The provisions of R.I. Gen. Laws Chapter 44-26, "Declaration of Estimated Tax by Corporations," shall apply to a combined group engaged in a unitary business - and to each member of such a group.B. Notwithstanding any other provisions of R.I. Gen. Laws § 44-26-2.1, any taxpayer required to file a combined return in accordance with R.I. Gen. Laws § 44-11-4.1 et seq. in a tax year beginning on or after January 1, 2015, shall compute estimated payments for that tax year as follows: 1. The installments must equal one hundred percent (100%) of the tax due for the prior year plus any additional tax due to the combined reporting provisions under R.I. Gen. Laws § 44-11-4.1; or2. The installments must equal one hundred percent (100%) of the current year tax liability.C. The provisions of § 10.18 of this Part shall also apply to affiliated groups making the federal consolidated group election for Rhode Island combined reporting purposes (as described in § 10.9 of this Part).280 R.I. Code R. § 280-RICR-20-25-10.18