Taxable perquisite calculation under annual accretion rules clarifies inclusion of employer contributions and income accrual. The rule prescribes a formula for computing annual accretion treated as a taxable perquisite under sub-clause (viia) of clause (2) of section 17. TP equals a prorated component of current principal contribution in excess of the employer contribution threshold plus a return component derived from prior principal contributions and prior taxable perquisites multiplied by an income-to-average-balance ratio R, where R equals income accrued in the current year divided by the average of opening and closing balances. A proviso excludes any excess of prior aggregates over the opening balance from TP1 and PC1 for computation.