Owed When Paid For?

When were future sins remitted by Christ’s payment on the cross? At the time of the payment, or later? Some think the payment was an inactive transaction which becomes activated with belief. However, it is what Christ did on Calvary that activates man's faith (because He bore the sin of unbelief - all sins), not that man's faith activates a transaction. He secured our salvation on the cross WHEN it was paid for (Col. 2:14).