@George4Tacks am I remembering  correctly that if the disposed of asset was in CA (or any other state with claw back rules) and the acquired asset is in another state, CA is only entitled to the deferred gain as determined at the time of the exchange, but not any additional gain since then?  If so, then the there is a reason to keep track of the deferred gain amount.

But I could be delusional about that.  It's been a bit since I've dealt with someone selling cross state asset with deferred gain.