339.6. For the purposes of section 339.5, the balance of the annuitized voluntary contributions of the taxpayer at the end of a taxation year is equal to the amount by which(a) such part of the aggregate of all amounts each of which is an additional voluntary contribution made by the taxpayer to a registered pension plan before 9 October 1986 in respect of services rendered by him before the year in which the contribution was made, to the extent that the contribution was not deducted in computing his income for any taxation year, as may reasonably be considered as having been used before 9 October 1986 to acquire or provide an annuity for the taxpayer’s benefit under a registered pension plan or registered retirement savings plan, or as having been transferred before 9 October 1986 to a registered retirement income fund under which the taxpayer was the annuitant, within the meaning of paragraph d of section 961.1.5, at the time of the transfer, exceeds
(b) the aggregate of all amounts each of which isi. an amount deducted in computing his income for a preceding taxation year under paragraph b of section 339.5, or
ii. an amount deducted in computing his income for the year or a preceding taxation year under paragraph a of section 339.5, to the extent that the amount can reasonably be considered to be in respect of a refund of additional voluntary contributions included in determining the aggregate under paragraph a.