Base invoice amount
 2.1 (1) The base invoice amount for a billing period in respect of an eligible account under this Part, (a)  includes, (i)  the commodity price of the electricity, (ii)  the rates and charges set out in the applicable rate order issued by the Board under subsection 78 (3) of the Ontario Energy Board Act, 1998, subject to clause (b), and (iii)  any adjustment on the invoice required pursuant to section 25.33 of the Electricity Act, 1998; (b)  does not include, (i)  the balance of any amounts carried forward from previous invoices, (ii)  all penalties and interest, (iii)  any charges that do not relate to the consumption of electricity, (iv)  the fixed monthly service charge payable by a generation facility, within the meaning of section 56 of the Ontario Energy Board Act, 1998, that is classified as “microFIT” in a rate order issued by the Board under subsection 78 (3) of that Act, (v)  charges labelled as “specific service charges” or “retail service charges” in the applicable rate order issued by the Board under subsection 78 (3) of the Ontario Energy Board Act, 1998, and (vi)  the amount of any harmonized sales tax payable under Part IX of the Excise Tax Act
(Canada). O. Reg. 342/19, s. 3. (2) Despite subsection (1), the base invoice amount for a billing period in respect of an eligible account with the following electricity vendors shall be determined as follows: 1.  If the invoice is issued by the IESO to a market participant who is a consumer, the base invoice amount for a billing period, i.  includes, A.  the commodity price of the electricity, B.  all settlement amounts appearing on the invoice in accordance with Chapter 9 of the market rules, C.  amounts payable by the market participant under subsection 79.1 (3) of the Ontario Energy Board Act, 1998, and D.  any adjustment on the invoice required pursuant to section 25.33 of the Electricity Act, 1998, and ii.  does not include anything listed under clause (1) (b). 2.  If the invoice is issued by Cornwall Street Railway Light and Power Company Limited, the base invoice amount for a billing period, i.  includes the cost of electricity supplied, including any delivery charges and regulatory charges, and ii.  does not include, A.  any charges for services that are not included in the cost of the electricity supplied, the delivery charges or the regulatory charges referred to in subparagraph i, and B.  anything listed under clause (1) (b). O. Reg. 342/19, s. 3. (3) The following amounts shall be included in the base invoice amount for a billing period as a credit: 1.  Rate assistance provided under the Ontario Electricity Support Program in respect of a billing period for which an invoice is issued before March 1, 2020. 2.  Any delivery credit provided under section 79.4 of the Ontario Energy Board Act, 1998. O. Reg. 342/19, s. 3; O. Reg. 16/20, s. 2. (4) An electricity vendor may make a reasonable estimate of, (a)  the volume of electricity used by a consumer during a portion of a billing period; and (b)  the portion of an amount that relates to electricity consumption during a portion of a billing period. O. Reg. 342/19, s. 3. (5) A base invoice amount for a billing period that would otherwise be less than zero is deemed to be zero. O. Reg. 342/19, s. 3.