(2) Limits on amounts which may be contributed (A) In general The amount of the designated nondeductible contributions made on behalf of any individual for any taxable year shall not exceed the nondeductible limit for such taxable year. (B) Nondeductible limit For purposes of this paragraph— (i) In general The term “nondeductible limit” means the excess of— (I) the amount allowable as a deduction under section 219 (determined without regard to section 219(g)), over (II) the amount allowable as a deduction under section 219 (determined with regard to section 219(g)). (ii) Taxpayer may elect to treat deductible contributions as nondeductible If a taxpayer elects not to deduct an amount which (without regard to this clause) is allowable as a deduction under section 219 for any taxable year, the nondeductible limit for such taxable year shall be increased by such amount. (C) Designated nondeductible contributions (i) In general For purposes of this paragraph, the term “designated nondeductible contribution” means any contribution to an individual retirement plan for the taxable year which is designated (in such manner as the Secretary may prescribe) as a contribution for which a deduction is not allowable under section 219. (ii) Designation Any designation under clause (i) shall be made on the return of tax imposed by chapter 1 for the taxable year.