336.7. No amount is deductible under section 336.6 in respect of an unused portion of the total investment expense for a taxation year until the unused portions of the total investment expense for the preceding taxation years have been deducted.
In addition, an unused portion of the total investment expense may be deducted for a taxation year under section 336.6 only if it exceeds the aggregate of the amounts deducted in its respect for the preceding taxation years under that section.