To have the ability to indicate for any account whether or not the account balance is included when calculating wealth tax. I think the default should be all accounts are included unless specifically excluded. Where an account is marked as excluded, perhaps the ability to specify what percentage (or value) of the account balance is to be excluded (this should provide for flexibility if things change in the future and the first X% is exempt etc).

The use case is UK tax payer calculating inheritance tax (wealth tax) at end of plan milestone event. In UK currently I believe any amounts held within a pension are excluded from inheritence tax calculations.

In this example all SIPP accounts would be flagged at excluded and 100% of the value excluded.