CAT aggregation rules
You pay Capital Acquisitions Tax (CAT) on the total of all the gifts or inheritances that you have received throughout your lifetime. The rules for how you add them are the aggregation rules.
Current CAT aggregation rules
These rules apply from 5 December 2001.
Aggregation rules for an inheritance or gift are those that apply at the date of death or the date of the gift. The valuation date, which determines the due date for CAT, is not relevant to aggregation rules.
To calculate the CAT on the latest benefit, add all inheritances or gifts received under the same group threshold from 5 December 1991:
Identify the group threshold applicable to the current benefit.
Add together the taxable value of all prior benefits received under this group threshold since 5 December 1991.
Calculate the unused balance of the group threshold.
Subtract this amount from the value of the current benefit.