11.5. For the purposes of the fourth paragraph of section 17.12 of the Act, a person referred to in that section may determine the amount of the refund to which the person is entitled by the formula
A/B × C.
For the purposes of this formula,
(a) A is the amount of the debt written off;
(b) B is the aggregate of the sales that are the amount of the debt to which the amount of the debt written off relates, including the amount provided for in section 17.2 of the Act, the tax payable under Part IX of the Excise Tax Act (R.S.C. 1985, c. E-15) and, where applicable, the tax payable under Title I of the Act respecting the Québec sales tax (chapter T-0.1);
(c) C is the amount provided for in section 17.2 of the Act, included in the aggregate of the sales that are the amount of the debt to which the amount of the debt written off relates.
Persons who wish to use the computation method provided for in the first paragraph in their fiscal year shall inform the Minister of such election using the prescribed form at the time of the initial application for a refund filed in that fiscal year. They shall also indicate therein the period covered by the fiscal year and use that method for the entire duration of that fiscal year.