776.1.22. No amount is deductible under section 776.1.21 in respect of an unused portion of the tax credit for a taxation year until the unused portions of the tax credit for the preceding taxation years that are deductible have been deducted.
In addition, an unused portion of the tax credit may be deducted for a taxation year under section 776.1.21 only to the extent that it exceeds the aggregate of the amounts deducted in its respect for the preceding taxation years under that section.