ADDITIONAL INCOME TAXES 113 with respect to the article otherwise than as an erroneous or illegal collection (assuming, in case the tax was not paid, that it had been paid). (c) The net income from the sales specified in subsection (a) (1) shall be computed as follows: (1) From the gross income from such sales there shall be de- ducted the allocable portion of the deductions from gross income for the taxable year which are allowable under the applicable Revenue Act; or (2) If the taxpayer so elects by filing his return on such basis, the total net income for the taxable year from the sale of all articles with respect to which each Federal excise tax was imposed (computed by deducting from the gross income from such sales the allocable portion of the deductions from gross income which are allowable under the applicable Revenue Act, but without deduction of the amount of such Federal excise tax which was paid or of the amount of reimbursement to purchasers with respect to such Federal excise tax) shall be divided by the total quantity' of such articles sold during the taxable year and the quotient shall be multiplied by the quantity of such articles involved in the sales specified in subsection (a) (1). Such quantities shall be expressed in terms of the unit on the basis of which the Federal excise tax was imposed. For the purposes of this section the proper apportionment and allo- cation of deductions with respect to gross income shall be determined under rules and regulations prescribed by the Commissioner with the approval of the Secretary. (d) The net income from reimbursement or refunds specified in subsection (a) (2) or (3) shall be computed as follows: From the total payment or accrual (1) of reimbursement to the taxpayer from vendors for amounts representing Federal excise tax burdens included in prices paid by the taxpayer to such vendors or (2) of refunds or credits to the taxpayer of Federal excise taxes erroneously or illegally collected, there shall be deducted the expenses and fees reasonably incurred in obtaining such reimbursement or refunds. (e) For the purposes of subsection (a) (1), (2), and (3) the extent to which the taxpayer shifted to others the burden of a Federal excise tax shall be presumed to be an amount computed as follows: (1) From the selling price of the articles there shall be deducted the sum of (A) the cost of such articles plus (B) the average margin with respect to the quantity involved; or (2) If the taxpayer so elects by filing his return on such basis, from the aggregate selling price of all articles with respect to which such Federal excise tax was imposed and which were sold by him during the taxable year (computed without deduction of reimburse- ment to purchasers with respect to such Federal excise tax) there shall be deducted the aggregate cost of such articles, and the differ- ence shall be reduced to a margin per unit in terms of the basis on which the Federal excise tax was imposed. The excess of such margin per unit over the average margin (computed for the same unit) shall be multiplied by the number of such units represented by the articles with respect to which the computation is being made; but (3) In no case shall the extent to which the taxpayer shifted to others the burden of the Federal excise tax with respect to the articles be deemed to exceed the amount of such tax with respect to such articles minus (A) the portion of the amount of the Federal excise tax (or of the reimbursement specified in subsection (a) (2)) with respect to the articles which is paid or credited by the, tax- payer to any purchasers as specified in subsection (f) (3) and
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